Lens barrel, camera and portable information terminal apparatus

ABSTRACT

A lens barrel includes a) a plurality of lens groups each having at least one lens, b) a plurality of lens retaining frames, including a retractable lens retaining frame, c) lens retaining frame driving devices, d) a main-guide shaft member in parallel to the optical axis to support the retractable lens retaining frame rotatably in longitudinal and circumferential directions of the main-guide shaft member, and e) a sub-guide shaft member to guide the retractable lens retaining frame along the optical axis and to allow the retractable lens retaining frame to be retracted toward the retracted position at a retracting point on the main-guide shaft member and to guide the retractable lens retaining frame on the main-guide shaft member along the optical axis at other than the retracting point. The retractable lens retaining frame is formed with an engaging portion to engage with the sub-guide shaft member and to be guided along the sub-guide shaft member, and the engaging portion being formed with an opened portion configured to allow the retractable lens retaining frame to be released from the sub-guide shaft member at the retracting point.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the priority benefit of Japanese PatentApplication 2005-064845 filed on Mar. 9, 2005, the entire contents ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a lens barrel which collapses lensgroups when in one state, and protrudes the lens groups to predeterminedpositions for use when in the other state. More particularly, thepresent invention relates to a lens barrel, a camera, a portableinformation terminal apparatus and an image pickup apparatus including alens barrel suitable for a zoom lens unit that can change a focaldistance by relatively moving a plurality of lens groups.

BACKGROUND ART

With improvement in high performance of a photographing lens such as azoom lens unit which is capable of changing the focal distance and indownsizing according to the user's demand as to an image pickupapparatus such as a digital camera, there are increasing types of imagepickup apparatus employing a so-called collapsing photographing lensunit in which lens cylinders are collapsed within a body of the imagepickup apparatus when photographing is not carried out. Furthermore,since not only a simple reduction in dimensions but also a furtherreduction in a thickness of the image pickup apparatus are alsodemanded, it is now important to reduce the thickness of the lens barrelportion in a collapsed state.

As a technology to cope with the demand for reduction in the thicknessof the image pickup apparatus, a construction has been used, in whichthe lens cylinders are collapsed into the body of the image pickupapparatus when the photographing is not carried out and in which a partof the lenses is evacuated from an optical axis of the lenses inphotographing, when the lens cylinders are collapsed. Such a technologyis disclosed, for example, in JP-A 2003-315861 and in JP-A 2003-149723.According to the structures disclosed in these Japanese unexaminedpatent application publications, since a part of the lenses is evacuatedfrom the optical axis when the lens cylinders are collapsed, thedimension of the entire lenses in a direction of the optical axis can bereduced in the collapsed state, so that the thickness of the imagepickup apparatus can be reduced.

However, in the structures disclosed in JP-A 2003-315861 and JP-A2003-149723, the position of the lens evacuated from the optical axis issubstantially within that lens cylinder which has the maximum outerdiameter. Therefore, the lens cylinders contribute to reduction inthickness of the image pickup apparatus when the lenses are collapsed,but the outer diameter of the lens barrel increases. When compared witha case where the lens is not evacuated from the optical axis, since theouter diameter of the lens cylinders increase, the dimensions of thelens cylinders, in particular, the dimensions of the lens cylinders asviewed in a plane orthogonal to the optical axis increase, As a result,there is a problem that the dimensions of the image pickup apparatus, inparticular, the dimension as viewed from a front side of the imagepickup apparatus increases.

RICOH. CO. LTD. proposed in Japanese Patent Application No. 2005-044909(not published) a lens barrel in which the thickness of an image pickupdevice can be made smaller without increasing the size of the imagepickup device. The lens barrel described in comprises a plurality oflens retaining frames holding a plurality of lens groups, respectively.Among the lens retaining frames, a retractable retaining frame isincluded, which is adapted to retract at least one lens of at least onelens group from the optical axis of the other lens groups when shiftinga collapsed state. The retractable lens retaining frame is supported, bymain-guide shaft member parallel to the optical axis of the other lensgroups, movably in a longitudinal direction of the main-guide shaftmember and rotatably around the axis of the main-guide member. Acompression torsion spring provided around the main-guide shaft membergives to the retractable lens retaining frame a rotation-urging forcetoward the optical axis of the other lens groups as well as an urgingforce in a collapsing direction along the optical axis.

The location of the optical axis of the lens retained by the retractablelens retaining frame on photographing is defined through the retractableretaining frame is defined when the retractable lens retaining frame isbrought into contact with an auxiliary shaft member, by means of therotation urging force of the spring, for guiding the retractable lensretaining frame along the optical axis of the other lens groups. On theother hand, the retractable lens retaining frame is turned around themain-guide shaft member against the rotation urging force of the springwhen being collapsed such that the lens retained by the retractable lensholding frame may be retracted outside the maximum outer diameter of thelens barrel. Thereby, the increase in the outer diameter of the lensbarrel can be more suppressed as compared with a conventional case inwhich the retracted position of the retracted lens is inside the maximumouter diameter of the lens barrel.

However, according to the invention described in Japanese patentapplication No. 2005-044909, the axis of the lenses is out of alignmenton photographing, when the retractable lens retaining frame receivesvibration and this vibration swings the retractable lens refrainingframe in direction of leaving the auxiliary guide shaft member over therotation urging force of the compression torsion spring. It may beconsidered that a restraining member is provided to prevent theauxiliary guide member of the restraint lens retaining frame onphotographing, vibration of the retractable lens retaining frame isprevented in the state that the retractable lens retaining frame is heldin between the restraining member and the auxiliary guide shaft member.In this case, the restraining member needs to be newly provided,resulting in completed construction.

SUMMARY OF THE INVENTION

Under the circumstances, the present invention is to provide a lensbarrel in which the optical axis of the retractable lens retained by theretractable lens retaining frame can be assuredly prevented from shakingon photographing by inhibiting the retractable lens retaining frame fromleaving the auxiliary guide shaft member on photographing, withoutproviding a new retraining member or thus resulting in complicatedconstruction.

DISCLOSURE OF THE INVENTION

The lens barrel according to the present invention, comprises:

a) a plurality of lens groups each having at least one lens;

b) a plurality of lens retaining frames each retaining corresponding oneof the plurality of the lens groups, said plurality of the lensretaining frames comprising a retractable lens retaining frame,

c) lens retaining frame driving devices configured to drive theplurality of the lens retaining frames,

said retractable lens retaining frame being configured to retain andmove at least one lens group such that the retractable lens retainingframe aligns the corresponding at least one lens group the other alongan identical optical axis in photographing state in which at least apart of the plurality of lens groups is moved toward a subject to bephotographed, and retracts said corresponding at least one lens groupoutside a telescopic cylinder containing therein the other lens groupsto a retracted position in a collapsed state in which at least a part ofthe plurality of the lens groups is collapsed to store the lens groups,said telescopic cylinder being constituted by movable lens cylinders forsaid the other lens groups, respectively;

d) a main-guide shaft member which is in parallel to said optical axisof the other lens group or groups and supports the retractable lensretaining frame rotatably in longitudinal and circumferential directionsof the main-guide shaft member, and

e) a sub-guide shaft member configured to guide said retractable lensretaining frame along the optical axis,

said sub-guide shaft member being configured to allow said retractablelens retaining frame to be retracted toward the retracted position at aretracting point on said main-guide shaft member and to guide saidretractable lens retaining frame on the main-guide shaft member alongsaid optical axis at other than the retracting point,

said retractable lens retaining frame being formed with an engagingportion configured to engage with the sub-guide shaft member and to beguided along the sub-guide shaft member, and said engaging portion beingformed with an opened portion configured to allow said retractable lensretaining frame to be released from the sub-guide shaft member at saidretracting point.

The following are preferred embodiments (1) to (7) of the lens barrelaccording to the present invention. Any combinations of the preferredembodiments are also preferred in the present invention, unless anycontrary occurs.

(1) Said movable lens cylinders retains said movable lens retainingframes therein, said movable lens retaining frames are driven by saidlens retaining frame driving device via said movable lens cylinders,respectively, and said retractable lens retaining frame retracts said atleast one retractable lens outside inner diameter portions of saidmovable lens cylinders at said retracting point.(2) The sub-guide shaft member is formed with a diameter-reduced portionat a position corresponding to said retracting point of said retractablelens retaining frame, said diameter-reduced portion being configured tobe released from the engaging portion through the opened portion.(3) A base portion of said sub-guide shaft member is fixed to astationary portion of a lens barrel body, and said diameter-reducedportion is formed near said base portion.(4) The lens barrel further comprises an urging device, and saidretractable lens retaining frame receives one direction rotation urgingforce toward the optical axis and an urging force toward a collapsingdirection along the optical axis from the urging device.(5) A digital camera comprises the lens barrel according to the presentinvention.(6) A mobile information terminal comprises the lens barrel according tothe present invention.(7) An image inputting device comprises the lens barrel according to thepresent invention.

According to the present invention, since the engaging portion providedin the retractable lens retaining frame is engaged with the sub-guideshaft member which is configured to allow said retractable lensretaining frame to be retracted toward the retracted position at theretracting point on said main-guide shaft member and to guide saidretractable lens retaining frame on the main-guide shaft member alongthe optical axis at other than the retracting point, the retractablelens retaining frame is allowed to move along the sub-guide shaft memberat other than the retracting point on the optical axis, while theretractable lens retaining frame is assuredly prevented from moving awayfrom the sub-guide shaft member. In addition, since the retractable lensretaining frame is allowed at the retracting point to move toward theretracted position by means of the opened portion formed in the engagingportion of the retractable lens retaining frame, no restraining memberis newly added to restrain the retractable lens retaining frame frommoving away from the sub-guide shaft member on photographing. Therefore,the retractable lens retaining frame can be assuredly prevented frommoving away from the sub-guide shaft member on photographing withoutcausing complicated construction due to the addition of such a newmember, so that shake of the optical axis of the retractable lensretained by the retractable lens retaining frame can be assuredlyprevented on photographing.

According to the construction of the preferred embodiment (1) of thepresent invention, the dimension of the lens barrel in the direction ofthe photographing optical axis can be effectively reduced withoutconspicuously increasing the size within the plane orthogonal to thephotographing optical axis.

According to the construction of the preferred embodiment (2) of thepresent invention, the diameter-reduced portion formed around thesub-guide shaft member at the position corresponding to said retractingpoint of said retractable lens retaining frame, said diameter-reducedportion can assuredly and smoothly release the engaging portion from thesub-guide shaft member through the opened portion.

According to the construction of the preferred embodiment (3) of thepresent invention, since the base portion of said sub-guide shaft memberis fixed to the stationary portion of the lens barrel body and saiddiameter-reduced portion is formed near said base portion, theretractable lens retaining frame can be assuredly moved to the retractedposition during the collapsing operation.

According to the construction of the preferred embodiment (4) of thepresent invention, since said retractable lens retaining frame receivesone direction rotation urging force toward the optical axis and anurging force toward a collapsing direction along the photographingoptical axis from the urging device, the retractable lens retained bythe retractable lens retaining frame can be stably operated with furthersimplified construction at a lower cost and a reduced space.

According to the construction of the preferred embodiment (5) of thepresent invention, the lens barrel according to the present invention isapplied to the digital camera. Therefore, the dimension of the digitalcamera in the direction of the photographing optical axis can beeffectively reduced without conspicuously increasing the size within theplane orthogonal to the photographing optical axis.

According to the construction of the preferred embodiment (6) of thepresent invention, the lens barrel according to the present invention isapplied to the mobile information terminal. Therefore, the dimension ofthe mobile information terminal in the direction of the photographingoptical axis can be effectively reduced without conspicuously increasingthe size within the plane orthogonal to the photographing optical axis.

According to the construction of the preferred embodiment (7) of thepresent invention, the lens barrel according to the present invention isapplied to the image inputting device. Therefore, the dimension of theimage inputting device in the direction of the photographing opticalaxis can be effectively reduced without conspicuously increasing thesize within the plane orthogonal to the photographing optical axis.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a perspective view showing a structure of a main part of anoptical system device, including a lens barrel according to a firstembodiment of the present invention with lens groups collapsed, as viewfrom a subject.

FIG. 2 is a perspective view showing the main part of the lens barrelshown in FIG. 1, as viewed from an imaging plane.

FIG. 3 is a schematic perspective view showing a structure of a mainpart of the optical system device including the lens barrel in which alens barrier is closed, as viewed from the subject.

FIG. 4 is a schematic perspective view showing the structure of the mainpart of the lens barrel shown in FIG. 3, as viewed from the imagingplane.

FIG. 5 is a schematic perspective view of the structure of the main partof the lens barrel in a state in which the lens barrier is opened in aphotographing state with the lens groups extended, as viewed from theimaging plane.

FIG. 6 is a perspective view of the structure of the main part of thelens barrel in the photographing state with the lens groups extended, asviewed from the imaging plane.

FIG. 7 is a perspective view of a layout of a third frame, an impactpreventing member, and a fourth frame in a state in which the lensgroups are in a collapsed position, for explaining operations of thethird frame which retains the third lens group and the impact preventingmember, as viewed from the subject.

FIG. 8 is a perspective view of a layout of the third frame, the impactpreventing member, and the fourth frame for explaining operations of thethird frame, which retains the third lens group, and theimpact-preventing member in the photographing state with the lens groupsprojected, as viewed from the subject.

FIGS. 9A and 9B are vertical cross sectional views showing, in an upperhalf and a lower half with respect to an optical axis, main parts of thelens groups, the lens retaining frames, and the various lens cylindersof the lens barrel in the photographing state, respectively, FIG. 9Ashowing the state that the lens groups are extended to a position inwhich the lens groups are extended to a telephotographic position, andFIG. 9B showing the state that the lens groups are projected to a mouthcorner.

FIG. 10 is a schematic development elevation view showing a shape of camgrooves formed on a second rotary cylinder in a developed state.

FIG. 11 is a schematic development elevation view showing a shape of camgrooves formed on a cam cylinder in a developed state.

FIG. 12 is a schematic development elevation view showing a shape of camgrooves and key grooves formed on a first liner in a developed statewith a helicoid omitted,

FIG. 13A is a schematic development elevation view showing a shape ofcam grooves and key grooves formed on a fixed frame in a developed statewith the helicoid omitted.

FIG. 13B is a schematic development elevation view with the helicoidadded.

FIG. 13C is a perspective view of an exterior appearance of a firstrotary cylinder to be fitted to a helicoid.

FIG. 14A is a side view showing a structure of the third frame and itsdrive system.

FIG. 14B is a perspective view of FIG. 14A.

FIG. 15 is a perspective view showing the structure of the third frameand its drive system.

FIG. 16A is a back view of the third frame portion for explainingoperation of the third frame, as viewed from the imaging plane.

FIG. 16B is a perspective view of mainly showing a shutter portion.

FIGS. 17A and 17B are perspective views showing an exterior appearanceand a structure of a camera according to a second embodiment of thepresent invention as viewed from the subject, in which FIG. 17A shows astate in which a photographing lens is collapsed in a body of thecamera, and FIG. 17B shows a state in which the photographing lens isprojected or extended from the camera body.

FIG. 18 is a perspective view schematically showing the exteriorappearance and structure of the camera of FIGS. 17A and 17B as viewedfrom a user.

FIG. 19 is a block diagram schematically showing a functional structureof the camera of FIGS. 17A and 17B.

FIG. 20A is a perspective view for schematically showing a structure ofa principal portion of the fourth lens retaining frame and its drivesystem.

FIG. 20B is a perspective view of FIG. 20A at a different angle with apart thereof omitted.

FIG. 21 is a block diagram schematically showing a construction of adrive control system.

FIG. 22 is a timing chart in a starting sequence in which a lens barrieris opened.

FIG. 23 is a timing chart in a starting sequence in which a lens barrieris operated from an opened position to a closed position.

FIG. 24 A is a table showing a reset sequence of the lens barrel.

FIG. 24 B is a timing chart of an H signal.

FIG. 25 is a timing chart showing a storage sequence in a state in whichthe lens barrier is closed.

FIG. 26 is a flow chart showing a zoom sequence.

FIG. 27 is a timing chart showing a zooming sequence from the wide angleto the telephoto in zooming.

FIG. 28 is a timing chart showing a zooming sequence from the telephototo the wide angle in zooming.

FIG. 29 is a perspective view of the third lens retaining frame at aposition on the photographing optical axis from the side of the object.

FIG. 30 is a plane view of an area shown by a two-dot chain line in FIG.29.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail, based on preferred embodiments ofthe present invention, to the accompanying drawings. Wherever possible,the same reference numbers are used in the drawings and the descriptionto refer to the same or like parts. The present invention, however, isnot limited to these embodiments. Within the scope of the presentinvention, any structure and material described below can beappropriately modified.

FIG. 1 to FIGS. 16A and 16B and FIGS. 20A and 20B illustrate a firstembodiment of a lens barrel according to the present invention.

In FIG. 1 to FIGS. 16(A) and 16(B) and FIGS. 20A and 20B, the lensbarrel includes a fixed frame 21 having a fixed cylinder 21 a, atelescopic cylinder unit or telescopic cylinder attached to the fixedframe 21, and a plurality of lens groups disposed in the telescopiccylinder. The telescopic cylinder is telescopically movable andcollapsible along an optical axis X of the plurality of lens groups. Thetelescopic cylinder is constituted by the fixed cylinder 21 a andmovable lens cylinders mentioned later.

Referring to FIGS. 9A and 9B, the lens groups comprise, for example, afirst lens group (movable lens) 11, a second lens group (movable lens)12, a third lens group (movable lens) 13, and a fourth lens group(movable lens) 14, which are disposed through an optical axis in thisorder in an image pickup state, as viewed from a side of an object. Ashutter/aperture unit 15 is inserted and disposed between the secondlens group 12 and the third lens group 13. A solid-state image sensingdevice 16 constituted by using CCD (Charge-Coupled Device) or isarranged at an imaging side of the fourth lens group 14. A focaldistance-variable lens is constituted by these first to fourth lensgroups 11 to 14. The first lens group 11 is constituted by at least onelens, and is fixedly held by a linearly-moving cylinder 27 via a firstlens retaining frame 17, which totally retains the first lens group 11.

The second lens group 12 includes one or more lens. A cam followerformed on a second frame (not clearly shown) for integrally retainingthe second lens group 12 is inserted into a cam groove, for the secondlens group 12, formed on the cam cylinder 26 shown in FIGS. 9 and 11,and engages with a linear groove 25 a of the second liner 25, and thesecond lens group 12 is supported by the cam cylinder 26 and the secondliner 25. The shutter/aperture unit 15 includes a shutter and anaperture, and a cam follower formed integrally with the shutter/apertureunit 15 is inserted into a cam groove for the shutter/aperture of thecam cylinder 26 shown in FIG. 11 and is engaged with the linear groove25 a on the second liner 25 so that the shutter/aperture unit issupported by the cam cylinder 26 and the second liner 25.

The fixed frame 21 includes a fixed cylinder having an inner surfacewhich is formed with a linear groove and a helicoidal cam groove alongan axial direction, as shown in FIGS. 13A and 13B. A helicoidal camfollower formed on an outer peripheral surface of a base portion of thefirst rotary cylinder 22 engages with the helicoidal cam groove, asshown in FIG. 13C, and a key portion projectedly formed on an innersurface of a base portion of the first liner 23 engages with the lineargroove of the fixed frame of the fixed frame 21. An inner surface of thefirst rotary cylinder 22 is formed with a guide groove extending along aplane transverse to the optical axis X. Engaged with the guide groove isa follower or key which is formed to project from the outer peripheralsurface of the first liner 23 in the vicinity of the base portionthereof and acts as a linear member. An inner surface of the first liner23 is formed with a linear groove along the optical axis and ahelicoids. In addition, the first liner 23 is formed with a clearancegroove in which a cam follower formed projecting from an outerperipheral surface of a base portion of the second rotary cylinder 24 inthe vicinity of the base portion is inserted.

A helicoid is formed on the outer peripheral surface of the base portionof the second rotary cylinder 24, and is engaged with the helicoid ofthe first liner 23. The cam follower formed projecting from the outerperipheral surface of the second rotary cylinder 24 in the vicinity ofthe base portion engages with the linear groove formed in the innerperiphery of the first rotary cylinder 22 through the clearance grooveof the cam follower on the first liner 23. A key portion formedprojecting from the outer peripheral surface of the base portion of thesecond liner 25 engages with the linear groove provided on the innerperipheral surface of the first liner 23. An inner surface of the secondrotary cylinder 24 is provided with a guide groove along a planetransverse to the optical axis, and a follower or key provided, as alinearly guiding member, projecting from the outer peripheral surface ofthe second liner 25 is engaged in the guide groove of the second rotarycylinder 24. With such a structure, the second liner 25 moves with thesecond rotary cylinder 24 in the movement along the optical axis, whilethe second rotary cylinder 24 is rotatable relative to the second liner25.

The cam cylinder 26 fitted to the inner periphery of the second liner 25is configured in such a manner that an engaging projection formed on theouter peripheral surface of the base portion is fitted to and engagedwith the base portion of the second rotary cylinder 24 so as to rotateintegrally with the second rotary cylinder 24. The inner surface of thesecond liner 25 is provided with a guide groove along a surfacetransverse to the optical axis X, and a follower or key projectedlyprovided, as a linearly guiding member, on the outer peripheral surface(front side) of the cam cylinder 26 engages with the cam groove. Withsuch a structure, the cam cylinder 26 moves with the second liner 25 inthe movement along the optical axis X, while is rotatable relative tothe second liner 25.

The base portion of the lineally-moving cylinder 27 is inserted betweenthe second rotary cylinder 24 and the second liner 25, and a camfollower is formed projecting from the outer peripheral surface of thelineally-moving cylinder 27 in the vicinity of the base portion, and thecam follower engages with the cam groove formed in the inner peripheralsurface of the second rotary cylinder 24. A linear groove is formed onthe inner peripheral surface of the lineally-moving cylinder 27 alongthe axial direction, and the key portion formed on the outer peripheralsurface of the second liner 25 engages with the linear groove. A gearportion is formed on the outer periphery of the base portion of thefirst rotary cylinder 22, the gear portion is engaged with one or moregears which are driven by a zooming motor 51 so that a drive force ofthe zooming motor 51 is transmitted to the gear portion via the gears,whereby the first lens group 11, the second lens group 12, and theshutter/aperture unit 15 are zoomed in a predetermined manner.

Meanwhile, the cam groove on the second rotary cylinder 24 engaging withthe cam follower on the linearly-moving cylinder 27 is shown in FIG. 10.The cam groove on the cam cylinder 26 which engages with the camfollower on the lens retaining frame of the second lens group 12 and thecam groove of the cam cylinder 26 which engages with the cam follower ofthe shutter/aperture unit 15 are shown in FIG. 11, respectively. The camgroove on the first liner 23 which engages with the cam follower of thesecond rotary cylinder 24 and the straight groove on the first liner 23which engages with the key portion on the second liner 25 are shown inFIG. 12. A linear groove on the fixed frame 21 engaging with the keyportion of the first liner 23 of the fixed frame and the cam groove ofthe fixed frame 21 engaging with the cam follower of the first rotarycylinder 22 are shown in FIG. 13.

Generally, the rotary cylinder, which is the closest position to thefixed frame and positioned on the outermost circumference is generallyscrewed onto the fixed frame through a helicoid, and the helicoid isconfigured to move the rotary cylinder at a constant speed relative tothe fixed frame. Therefore, the rotary cylinder is in a half-extendedstate out of the fixed frame in a short focal length/wide angle positionin a course in which the rotary cylinder is moved gradually from thecollapsible position through the short focal length/wide angle positionto a long focal length/telephoto position. On the contrary, in thestructure described above, the first rotary cylinder 22 is threaded withthe fixed cylindrical portion of the fixed frame 21 via the cam grooveof the helicoidal shape without a simple helicoidal connection. Thefirst rotary cylinder 22 is moved completely to the maximally extendedposition by being driven from the collapsible or collapsed position tothe short focal length/wide angle position. Thereafter, as shown in FIG.13, because the subject side end of the cam groove lies in parallel withthe end surface of the fixed cylindrical portion, the first rotarycylinder 22 rotates at a constant position without moving along theoptical axis X during driving from the short focal length/wide angleposition to the long focal length/telephoto position.

As the first rotary cylinder 22 is moved from the collapsible positionto the short focal length/wide angle position first under rotation in anearly stage of drawing out action, it is extended to the side of thesubject. After the rotary cylinder 22 reaches the maximally extendedposition, a zoom position reference-signal is generated by a zoomposition detector which is provided on the fixed frame and comprising aphoto-reflector, a photo-interrupter, a leaf switch or the like, forexample. Thus, when the zoom position reference-signal is generated, itmay be determined that the first rotary cylinder 22 reaches themaximally extended position. The retractable lens retaining frame, thatis, the third lens retaining frame 31 in this embodiment, begins toenter toward the photographing optical axis.

Consequently, a space is previously ensured to insert the third lendgroup 13 into the photographing optical axis by completely drawing outthe first rotary cylinder 22 and the first liner 23 adjacent to thefixed frame at the earlier step of the extended action.

As described below, as soon as the first rotary cylinder 22 reaches themaximally extended position, the zoom position-reference signalgenerates, the space for inserting the third lens group is secured, andimmediately, the insertion of the third lens group is initiated.Therefore, a time from the collapsible position when an electric sourceis turned on to the short focal length/wide angle position can be muchshortened.

The retractable third lens group 13 is retained to the third frame 31 orretractable lens retaining frame. The third frame 31 retains the thirdlens group 13 at one end thereof, and the other end of the third frame31 is supported by a third group main-guide shaft 32 which extendssubstantially in parallel with the optical axis of the third lens group13 so as to be capable of rotating, and sliding along the third groupmain-guide shaft 32. The third frame 31 is rotatable about the thirdgroup main-guide shaft 32 between a setting position in which the thirdlens group 13 is disposed onto the optical axis or the photographingoptical axis in a photographing state, as shown in FIG. 8 and theretracted position in which the third lens group 13 is retracted out ofthe telescopic cylinder in the fixed frame 21, as shown in FIG. 2. Inthe vicinity of the third lens group 13 on the side of the rotating endof the third frame 31, a crank-shaped bent portion is formed in thisembodiment for differentiating the position of the third lens group 13in the direction parallel with the main-guide shaft between the side ofthe rotation axis and the side of the supporting portion, a stopper 31 a(FIG. 15) and a light-shielding strip 31 b are provided on the rotatingend to project from the bent portion substantially toward the rotatingend.

On the optical performance, in order to lengthen a focus length in thetelephoto state, a position of the third lens group 13 in the telephotostate is in an extended position closer to the subject. However, apossible moving amount of the third frame 31 is determined by limitationof a length of the lens barrel in the collapsed state along the opticalaxis. It is possible to maximize the focus length in the telephoto stateby setting a position for retaining the third lens group by the thirdframe 31 in the closest position to the subject. However, if a positionof the stopper 31 a along the optical axis sets on the generally sameposition as the third lens group 13 at the side of the subject, a lengthof a third frame sub-guide shaft 33, which defines the position of theoptical axis of the third lens group 12 retained in the third frame 31upon receipt of the stopper 31 a is longer and a size of the lens barrelin the collapsible position becomes greater. Therefore, it is requiredthat the stopper 31 a is set on a side of a focusing position as near aspossible and the third frame 31 is formed into a shape having thecrank-shaped bent portion. Meanwhile, the third frame 31 may be formedfrom two parts and in this case, one is a member having the crank-shapedbent portion, the other is a member for retaining the third lens group13. The two parts operates integrally by being fixed together.

As shown in FIGS. 14A and 14B, a third frame female screw member 35screwed on a third group lead screw 34 is positioned in the closestposition to an image plane of the CCD in the retracted state in whichthe third frame 31 is retracted. In this state, a compression torsionspring 37 is charged or compressed fully so as to impart constantly aclockwise (direction for the third frame to move toward the opticalaxis) moment as viewed from the front of the lens barrel to the thirdframe 31. A cylindrical outer peripheral surface of a supported partprovided on the main-guide shaft 32 for the third frame 31 is providedwith a stepped portion 31 c, and a cam portion 31 e disposed inside thestepped portion 31 c and formed from an inclined surface, as shown inFIG. 14A. From this state, when a third frame drive motor 52 is rotatedclockwise as viewed from the front of the lens barrel, the third grouplead screw 34 is rotated clockwise through a gear mechanism includinggears 71 to 74, and the third frame female screw member 35 moves towardthe subject along the optical axis X. At this time, the third frame 31is rotated clockwise by a moment force of the compression torsion spring37, the cam portion 31 e engages with a first abutting portion 35 aprovided on the third frame female screw member 35. Thereafter, when thethird frame female screw member 35 is moved in the engaged position tothe side of the subject, the light-shielding strip 31 b of the thirdframe 31 is turned around the main-guide shaft 32 up to a position outof a third frame photo-interrupter 38 as a device for detecting aposition of the third lens group 13, thereby the third framephoto-interrupter 38 generates a reference signal in a range from L or alow level to H or a high level. Accordingly, a position of the thirdlens group 13 is controlled by pulse count based on the reference signalfrom the third frame photo-interrupter 38.

From this state, when the third frame female screw member 35 is moved toa retract-initiating position B of the third frame 31, as shown in FIG.14A, the third frame 31 further rotates clockwise, the stopper 31 acomes into abutment with the third frame sub-guide shaft 33 as shown inFIGS. 8 and 16A, as a result, a position of the third group lensretained by the third frame 31 on the optical axis is determined.Consequently, approach operation of the third lens group 13 to theoptical axis is completed. In the retract-initiating position B, thethird frame 31 is movable toward the retracted position S. Meanwhile,the light-shielding strip 31 b shields the third frame photo-interrupter38 shown in FIG. 16 A so that it is possible to confirm that the thirdframe 31 is in the retract-initiating position B. When the third framefemale screw member 35 is moved to the retract-initiating position Bshown in FIG. 14A, the first abutting portion 35 a of the third framefemale screw member 35 contacts with a front engaging portion 31 d ofthe stepped portion 31 c of the third frame 31. Again, the steppedportion 31 c of the third frame 31 has the cam portion 31 e and thefront engaging portion 31 d which forms a planner surface generallyperpendicular to the third group main-guide shaft 32. The steppedportion has a recessed shape in the cylindrical peripheral face. Thethird frame 31 is constantly biased to move to a direction transverse tothe optical axis, that is to say, from the retracted position to theoptical axis and a rotating direction toward the optical axis, that isto say, from the subject to a retainer plate 81 beside the image planeby the compression torsion spring 37 provided on the third groupmain-guide shaft 32.

In addition, a portion of the fixed frame 21 on which the compressiontorsion spring 37 is pushed includes a step 37 a which is formed as aconcave portion for inserting one end of the compression torsion spring37, as shown in FIG. 14B, to prevent the compression torsion spring fromdeviating out of a center of the third group min-guide shaft 32considerably.

Next, when the third frame female screw member 35 is moved to a shortfocal length/wide angle position such as a wide angle position W shownin FIG. 14A, because the first abutting portion 35 a of the third framefemale screw member 35 presses the front engaging portion 31 d, thethird frame 31 is movable to the wide angle position along the opticalaxis X toward the subject.

Moreover, while the third frame female screw member 35 is disposedbetween the retract-initiating position B and a telephoto position T, asshown in FIG. 14A, because the third frame 31 is constantly pressedalong the optical axis toward the image plane by the compression torsionspring 37, all spaces generated among the third group lead screw 34, thethird frame female screw member 35 and the retainer plate 81 aredirected to the image plane, the third frame 31 can secure a positionalaccuracy in the direction of the optical axis.

The third frame female screw member 35 is screwed on the third grouplead screw 34 disposed substantially in parallel with the optical axis.The third frame female screw member 36 includes a rotation-preventingprojection 35 b in addition to the first abutting portion 35 a, whichengages with the above-described front engaging portion 31 d or the camportion 31 c of the third frame 31. The rotation-preventing projection35 b is fitted slidably into a guide groove formed on the cylindricalpart of the fixed frame 21 in parallel with the optical axis as arotation-preventing device for preventing the third frame female screwmember 35 from rotating along with the rotation of the third lead screw34. In other words, the third frame female screw member 35 is moved inthe back and forth direction along the optical axis by the rotation ofthe third lead screw 34, because the third frame female screw member 35is prevented from rotating by the rotation-preventing projection 35 bfitting into the guide groove of the fixed frame 21.

As shown in FIG. 14A in detail, when the third frame female screw member35 is moved further toward the image plane (left side in the drawing)from the retract-initiating position B shown in FIG. 14A, the thirdframe female screw member 35 engages with the cam portion 31 e of thestepped portion 31 c the third lend group-retaining frame 31. The thirdframe 31 comes into contact with the retainer plate 81 by a biasingforce of the compression torsion spring 37 clockwise, the third frame 31is rotated counterclockwise against the clockwise biasing force exertedby the compression torsion spring 37, and therefore the third frame 31can be retracted.

On the other hand, while the third frame female screw member 35 is movedfrom the telephoto position T through the wide angle position W to theretract-initiating position B by the reverse rotation orcounterclockwise rotation of the third group lead screw 34, because thefirst abutting portion 35 a of the third frame female screw member 35engages with the front engaging portion 31 d of the stepped portion 31 cof the third frame 31, the third frame 31 moves gradually to direct fromthe side of the subject toward the image plane while maintaining aposition on the optical axis limited by the third frame sub-guide shaft33 by the biasing force toward the optical axis and the biasing forcetoward the image plane. Meanwhile, when the third frame female screwmember 35 reaches the retract-initiating position B, a base end surface31 f of the third frame 31 abuts with the retainer plate 81, the thirdframe female screw member 35 is disposed with an interval from the frontengaging portion 31 d and contacts with the cam portion 31 e of thestepped portion 31 c.

While the third frame female screw member 35 moves from theretract-initiating position B to the collapsed position S, the secondabutting portion 35 c of the third frame female screw member 35 comesinto sliding contact with the cam portion 31 e of the stepped portion 31c of the third frame 31 and rotates the third frame 31 against therotational biasing force exerted by the compression torsion spring 37,whereby the third frame 31 moves from the position on the optical axisto the collapsed position S. The collapsed position S of the third frame31 corresponds to a position at which it is moved toward the image planeby a predetermined pulse count number after the generation of thereference signal of the range from the H to the L generated from thethird frame photo-interrupter 38. After the third frame 31 is moved tothe collapsed position S, the first lens group 11, the second lens group12, and the shutter/aperture unit 15 are allowed to be moved to thecollapsible or collapsed position.

In this example, before the third frame 31 is moved to the collapsedposition S, a fourth frame 41 for retaining the fourth lens group 14 isfirst moved to the collapsed position. A first collapsed position of thefourth frame 41 corresponds to a position at which it is moved towardthe image plane by a predetermined pulse count number after thegeneration of a storage reference signal of a range from the H to the Lgenerated by a fourth group reference detector or fourth groupphoto-interrupter 47. After the fourth frame 41 reaches the firstcollapsed position, the third frame 31 is initiated to be stored.

That is to say, the third frame female screw member 35 moves toward theimage plane by a predetermined pulse count number from the generation ofthe stored reference signal from the H to the L by the third framephoto-interrupter 38 (see FIG. 16A) and the stored operation of thethird frame 31 is completed. After the completion of the storedoperation of the third frame 31, the first rotary cylinder 22 is storedor structural parts disposed inside the first rotary cylinder 22 and thefirst liner 23, that is, the structural parts at the forward positionfrom their base end faces, are stored from the position immediatelybefore contacting with the third frame 31. This results in the safestorage of the first rotary cylinder 22 and so on without interferingwith the third frame 31. Positions of the first rotary cylinder 22 andso on can be set by a drive pulse count generated by a zoom countdetector comprising a pinion gear attached directly to an output shaftof the zooming motor 51 and having an encoder structure and for example,a first and second frames photo-interrupter 41 a disposed adjacent thepinion gear, for example. Meanwhile, although the DC motor is used asthe drive source for moving the first rotary cylinder 22 and the driveposition of the first rotary cylinder 22 is detected by the detectorcomprising the encoder and the photo-interrupter, in the above-mentionedexample, the similar function can be accomplished by substituting apulse motor structure for the whole of the above-mentioned structure.

To prevent the third frame 31 from collision with the other parts, animpact-preventing member 36 is, as shown in particular in FIGS. 2 and 7,rotatably supported on the fixed frame 21 in the vicinity of the thirdgroup main-guide shaft 32 and includes a rotated portion provided at oneend of the impact-preventing member and an engaging projection 36 a neara rotating end. The impact-preventing member 36 is constantly biased tocause the engaging projection 36 a to move toward the photographingoptical axis X by a spring or the like. When the third frame 31 ispositioned in the collapsed position, the impact-preventing member 36 ispushed out by a rotating force of the third frame 31 against a biasingforce of the spring, and is deviated outside the third frame 31 (seeFIG. 2 and FIG. 7, specifically). When the third frame 31 is rotated andpositioned on the optical axis, the impact-preventing member 36 isreleased from engagement with the third frame 31, and is rotated tocause the engaging projection 36 a to be projected toward the opticalaxis X by the biasing force, thereby causing the engaging projection 36a to project from the inner surface of the fixed frame of the fixedframe 21. At this time, in addition to the first rotary cylinder 22 andthe first liner 23, the second rotary cylinder 24, the second liner 25,the cam cylinder 26 and the lineally-moving cylinder 27 are allpositioned on the subject side with respect to the projected position ofthe engaging projection 36 a. Therefore, the engaging projection 36 a ispositioned to project inwardly of an outer peripheral edge of the baseportion of each of the first rotary cylinder 22 and the first liner 23(see FIG. 5, FIG. 6, and FIG. 8, specifically).

With such a structure, even if an operator rotates the first rotarycylinder 22 manually forcibly and moves it to the collapsed position,the impact-preventing member 36 first contacts with the first rotarycylinder 22. Therefore, because the base portion of the first rotarycylinder 22 cannot be moved toward the image plane than the position ofthe impact-preventing member 36 along the optical axis, the first rotarycylinder 22 is prevented from contacting with the third frame 31.Accordingly, it is possible to accomplish the prevention of breaking,damage or the like of the third frame 31 due to a strength externalforce. In addition, the first rotary cylinder 22 can be first moved tothe collapsed position after the third frame 31 is moved completely tothe collapsed position correctly.

Therefore, in a used or photographing state of the lens barrel, in whichthe movable cylinders such as the first rotary cylinder 22 and so on areextended, when a great pressure is exerted on a leading end of the lensbarrel and so on by a drop of the lens barrel or the like, the engagingprojection 36 a of the impact-preventing member 36 engages with thefirst rotary cylinder 22 and the first liner 23, and hence furtherretraction of the first rotary cylinder 22 and the first liner 23 (aswell as the second rotary cylinder 24, the second liner 25, the camcylinder 26, and the lineally-moving cylinder 27) toward the third lensgroup 13 is prevented, so that the third frame 31 and the third lensgroup 13 are prevented from being damaged.

The third group lead screw 34 is rotated in forward and reversedirections by a third frame drive motor 52. The rotation of the thirdframe drive motor 52 is transmitted to the third group lead screw 34 viagears 71, 72, 73, and 74 arranged in sequence.

Next, a drive structure of the fourth lens group 14 is explained withreference to FIGS. 7 and 8, and FIGS. 20A and 20B being perspectiveviews showing the fourth lens group driving system.

The fourth lens group 14 used as a focusing lens for focusing the lensgroups in the illustrated embodiment is retained by the fourth frame 41,as shown in FIGS. 20A and 20B. The fourth frame 41 includes a sleeveportion 41 a in which the fourth frame main-guide shaft 44 disposed inparallel with the optical axis and fixed to a lens barrel base 82 isfitted, and a rotation-preventing portion 41 b in which the fourth framesub-guide shaft 42 disposed in parallel with the optical axis and fixedto the lens barrel base 82 is fitted, to limit the rotation of thefourth frame 41. With such a structure, the fourth frame 41 can be movedfreely along the fourth frame main-guide shaft 44 or the optical axis. Afourth frame drive motor 53 comprising a stepping motor is used as adrive source for driving the fourth frame 41 in the illustratedembodiment. Provided on an output shaft of the fourth frame drive motor53 is a fourth frame lead screw 45 which is threaded into a threadedhole provided in a fourth frame female screw member 46.

The fourth frame 41 has an opening for inserting the fourth frame femalescrew member 46. The opening has an engaging portion 41 c for engagingwith the fourth frame female screw member 46 in a perpendicular plane tothe optical axis in a side of the image plane. The fourth frame 41 isalways engaged with the fourth frame female screw member 46 by allowingthe fourth frame 41 to bias to the subject by a fourth frame spring 43.The fourth frame female screw member 46 has a radially projectedprotrusion 46 a. The protrusion 46 a is engaged in a bore 41 d providedin one side of the opening for inserting the fourth frame female screwmember 46 of the fourth frame 41 so that the rotation of the fourthframe female screw member 46 is stopped.

In this way, when the fourth frame drive motor 53 which is the steppingmotor is driven, the fourth frame lead screw 45 rotates, the fourthframe female screw member 46 is moved in the forward and reversedirections along an axis of the fourth frame lead screw 45 or theoptical axis X. Because the fourth frame 41 engages with the fourthframe female screw member 46, the fourth frame 41 is moved along theoptical axis following to the movement of the fourth frame female screwmember 46. In this case, although the fourth frame lead screw 45 isformed on the output shaft of the fourth frame drive motor 53, thefourth frame lead screw 45 may be rotated by constituting the fourthframe drive motor 53 and the fourth frame lead screw 45 separately andconnecting them through gears or the like.

The fourth frame 41 is provided with a light-shielding piece 41 e whichshields an optical passage of a fourth group photo-interrupter 47provided on the lens barrel base 82, the light-shielding piece 41 e iscapable of light-shielding or passing light through the optical passageof the fourth group photo-interrupter 47 in response to the movement ofthe fourth frame 41. In this case, the fourth frame 41 can be moved in apredetermined position by recognizing as a reference position a time atwhich the light-shielding pieces is set from the light-shielding stateto the light-passing state, energizing a pulse waveform of any pulsenumber from the reference position, rotating the fourth frame drivemotor 53.

Meanwhile, the fourth frame 41 has a concave portion 41 f which isprovided in an outer peripheral edge thereof and allows thelight-shielding member 31 b of the third frame 31 for thephoto-interrupter 38 to move toward the optical axis to avoid theinterference with the fourth frame 41, thereby the movement amount ofthe fourth frame 41 can be increased and a range capable of focusing canbe enlarged. Moreover, as described above, there is a clearance betweenthe fourth frame 41 and the fourth frame female screw member 46 in thedirection of the optical axis, but the position in the direction of theoptical axis of the fourth frame 41 can be controlled accurately byconstantly biasing the fourth frame 41 toward the subject by the fourthframe spring 43.

The collapsed position of the first rotary cylinder 22, the first liner23, the first lens group 11, the second lens group 12, and theshutter/aperture unit 15 is controlled based on the zoomposition-reference signal generated by the zoom position detectorcomprising the photo-reflector and so on disposed in the fixed frame 21.That is to say, it is possible to complete the storing operation bymoving them toward the image plane by the predetermined pulse countnumber of the drive pulse generated by the pinion gear acting as theencoder and the zoom count detector disposed adjacent to the pinion gearafter the change of from the H to the L of the zoom position storagereference signal occurs. In storing, the fourth frame 41 is positionedin the first collapsed position as described above, while, when thefirst rotary cylinder 22 is moved to the collapsed position, the mostdistal surface of the first rotary cylinder 22 or the first liner 23contacts with the fourth frame 41 and presses the fourth frame 41 tomove to the second collapsed position finally. By such an operation,even if variations of the attached position of the fourth groupphoto-interrupter 47 in the direction of the optical axis occur, thefourth frame 41 can be moved to the collapsed position accuratelywithout requiring a complicated adjustment. Such an operation can beaccomplished for the reason that a length of the engaging space formedin the fourth frame 41, in the direction of the optical axis is largerthan a thickness of the fourth frame female screw member 46.

The zooming motor 51 for moving the first lens group 11, the second lensgroup 12, and the shutter/aperture unit 15 is structured by the DC motorfor example as described above in the illustrated embodiment. The thirdframe drive motor 62 for driving the third lens group 13 and the fourthframe drive motor 53 for driving the fourth lens group 14 are generallyconfigured to use a pulse motor for example. The zooming motor 51, thethird frame drive motor 52 and the fourth frame drive motor 53 aredriven in conjunction with each other in a software-like manner toachieve an appropriate zooming action performed mainly by the first tothe third lens groups 11–13 and an appropriate focusing action performedmainly by the fourth lens group 14, for example.

Now, a drive control system for the lens groups structuring the lensbarrel is described in detail with reference to FIGS. 21 to 28.

The drive control system is shown in FIG. 21. The drive control systemincludes the central calculation processing device 601, a motor driver502, a first and second frames DC motor 503, a first aperture stop motor504, a second aperture stop motor 505, a shutter motor 506, a thirdframe pulse motor 507, a fourth frame pulse motor 508, a first andsecond frames photo-interrupter 509, a first and second framesphoto-reflector 510, the third frame photo-interrupter 511, a fourthframe photo-interrupter 512, a first and second frames photo-interrupterdrive circuit 513, a first and second frames photo-reflector drivecircuit 514, a third frame photo-interrupter drive circuit 515, and afourth frame photo-interrupter drive circuit 516.

The central calculation processing device 501 gives a command such as aninitial setting of the motor driver 502, the selection for a drivemotor, the setting of a drive voltage, a direction for driving and soon, to the motor driver 502. The motor driver 502 controls the motorsystem of the first and second frames DC motor 503, the first aperturestop motor 504, the second aperture stop motor 505, the shutter motor506, the third frame pulse motor 507, the fourth frame pulse motor 508and so on, in accordance with the command from the central calculationprocessing device 501. The first and second frames DC motor 503 drivesthe first and second lens groups 11 and 12. As always, the first andsecond groups 11 and 12 are driven separately with respect to each otherthrough a cam mechanism in response to the drive of the first and secondframes DC motor 503. The first aperture stop motor, 504 and the secondaperture stop motor 505 are configured to drive an aperture stop of theshutter/aperture unit 15. The shutter motor 506 drives a shutter of theshutter/aperture unit 15. The third frame pulse motor 507 drives thethird lens group 13. The fourth frame pulse motor 508 drives the fourthlens group 14.

The central calculation processing device 501 supplies a driveelectricity to the first and second frames photo-interrupter 509, thefirst and second frames photo-reflector 510, the third framephoto-interrupter 511, and the fourth frame photo-interrupter 512 as thedevice for detecting position through the first and second framesphoto-interrupter drive circuit 513, the first and second framesphoto-reflector drive circuit 514, the third frame photo-interrupterdrive circuit 515, and the fourth frame photo-interrupter drive circuit516. The central calculation processing device 501 also acquires apositional information signal detected by the first and second framesphoto-interrupter 509, the first and second frames photo-reflector 510,the third frame photo-interrupter 351, and the fourth framephoto-interrupter 512. The first and second frames photo-interrupterdrive circuit 513, the first and second frames photo-reflector drivecircuit 514, the third frame photo-interrupter drive circuit 515, andthe fourth frame photo-interrupter drive circuit 516 have a function tocontrol suitably a level of a projecting current and an output signal ofeach of the first and second frames photo-interrupter 509, the first andsecond frames photo-reflector 510, the third frame photo-interrupter511, and the fourth frame photo-interrupter 512. The motor driver 502receives a command from the central calculation processing device 501and executes the command. The central calculation processing device 501sets a designated voltage to one or more selected motors of the firstand second frames DC motor 503, the first aperture stop motor 504, thesecond aperture stop motor 505, the shutter motor 506, the third framepulse motor 507, the fourth frame pulse motor 508, and controls them inaccordance with a timing of drive command.

<Activation Sequence>

An activation sequence of the above-mentioned drive control system isexplained with reference to FIG. 22.

By opening the lens barrier 62, a barrier switch signal (barrier SW)from a barrier switch (not shown) changes from the H to the L and aninitial setting of the lens barrel is initiated. Meanwhile, the barrierswitch is operated by opening mechanically the lens barrier 62 with anoperating lever or the like (not shown), while the lens barrier may beopened by operation of the barrier switch. Executing of the initialsetting causes the initialization of the motor driver 502 for drivingthe motor system, and also causes the initialization of the first andsecond frames photo-interrupter 509, the first and second framesphoto-reflector 610, the third frame photo-interrupter 511, and thefourth frame photo-interrupter 512, as the position detecting deviceswhich detect positions through the first and second framesphoto-interrupter drive circuit 513, the first and second framesphoto-reflector drive circuit 514, the third frame photo-interrupterdrive circuit 515, and the fourth frame photo-interrupter drive circuit516.

In the case that detected results by the first and second framesphoto-interrupter 509, the third frame photo-interrupter 511, and thefourth frame photo-interrupter 512 indicate the collapsed position, thefirst and second frames DC motor 503 is adapted to be driven toward thewide angle position. A driven amount of the first and second frames DCmotor 503 is detected by the first and second frames photo-interrupter509 for detecting the moving amount of the first and second lens groups.The moving amount is detected by counting edge portions of the pulsesignal (PI signal) by the first and second frames photo-interrupter 509.

During an activation period immediately after the first and secondframes DC motor 503 is activated, the drive voltage is set to be lowerthan a constant voltage so as to prevent a rush current by the DC motor.After the activation period is completed, the drive voltage is increasedto a stationary voltage.

A period for monitoring the barrier switch (barrier SW) immediatelyafter the initiation of the activation of the first and second frames DCmotor 503 is set and a state of the barrier switch signal is monitoredby the central calculation processing device 501. During the monitoringperiod, if the barrier switch signal indicates the opening state of thelens barrier, the shutter is set in the full opening by theshutter-motor 50 for driving the shutter. Then, the aperture stop is setin an intermediately restricted state by the first and second, aperturestop motors 504 and 505. In this example, although the aperture stop isset in the intermediately restricted state, the aperture stop may be setin an opened state (fully opened state).

Subsequently, the fourth lens group 14 is previously driven through thefourth pulse motor 508. By achieving the previous drive of the fourthlens group 14, the total time from the initiation of the drive of thefirst and second lens groups to the completion of the drive of the finalfourth lens group 14 can be reduced. Moreover, it is possible to greatena torque when driving and thereby to prevent the interference of thefourth lens group with the other parts by setting a pulse rate of thefourth frame pulse motor 508 in the previous drive thereof lately thanthat in the normal driving state.

Meanwhile, the driven amount of the fourth lens group by the fourthframe pulse motor 508 is set so that the third and fourth lens groupsmay not interfere with each other.

When the previous drive of the fourth lens group 14 is completed, thewaiting for the reference position detection by the first and secondframes photo-reflector 510 is set. A place where the reference positionsignal (HP signal) changes from the H to the L becomes the referenceposition (HP position) of the first and second lens groups 11 and 12.When the reference position (HP position) of the first and second lensgroups 11 and 12 is detected, positional information of the first andsecond lens groups 11 and 12 is reset. In this embodiment, the HPpositions of the first and second lens groups 11 and 12 are configuredto be detected by way of detecting the position of first and secondframes. The movement of the first and second lens groups 11 and 12 iscontrolled by counting the pulse-like signal (PI signal) by the firstand second frames photo-interrupter 609 so as to acquire the movementamount of the first and second lens groups 11 and 12 based on thepositional information to the wide angle position. The wide angleposition is previously set, but it can be changed by storing it in anonvolatile memory such as an EEPROM (Electronically Erasable andProgrammable Read Only Memory) or the like and rewriting it.

A specified pulse period before reaching the wide angle position is astop controlling period, in which the drive voltage is lowered inaccordance with residual pulse numbers to the wide angle position so asto reduce overrun in reaching the wide angle position. If the first andsecond lens groups reach the wide angle position by counting the PIsignal by the first and second frames photo-interrupter 509, a brakingcontrol is made in order to stop the first and second lens groups. Anamount of overrun during the braking period is also counted to decidethe final position of the first and second lens groups 11 and 12.

Moreover, when the reference position (HP position) of the first andsecond lens groups 11 and 12 is detected, the drive of the third framepulse motor 607 in the direction of wide angle position is initiated tocontrol the third lens group 13 with the first and second lens groups 11and 12. The driving time of the third lens group 13 can be reduced bysetting the pulse rate in driving the third group pulse motor highly orrapidly than that in the normal drive.

In the third lens group 13, as described above, the retracted position(in the retracted state) of the third frame 31, the optical axisentrance completed position of the third frame-31 at the time that thestate has changed from the retracted state to the photographable state,and the distance from the reference position or the position of thethird frame 31 in the photographable state in which the focal distanceduring the wide-angle photographing and the telephoto photographing ischanged, are detected by the position detector structured by theT-shaped protruded member 350 or the L-shaped protruded member 362 andthe transmissive photo-interrupter 351. More specifically, the thirdlens group 13 is waited for detecting the reference position by thethird frame photo-interrupter 351. The position at which thepredetermined number of pulses from the place where the referenceposition signal (HP signal) detected by the third framephoto-interrupter 351 has changed from the L to the H is detectedbecomes the reference position (HP position) of the third lens group 13.In this embodiment, the HP position of the third lens group 13 isconfigured to be detected by way of detecting the position of the thirdframe 31. When the reference position (HP position) is detected,positional information of the third lens group 13 is reset. The thirdlens group 13 is pulse-driven according to the movement amount to thewide angle position by the third frame pulse motor 507 on the basis ofthe detected position (HP position). The wide angle position ispreviously set, but it can be changed by storing it in the nonvolatilememory such as the EEPROM or the like and rewriting it.

In addition, the final stopping position of the third lens group 13 isthe position in which the overrun of the first and second lens groups 11and 12 is considered. That is to say, because the stopped position ofthe first and second lens groups 11 and 12 is “the wide angle positionplus the overrun amount” due to the overrun, the stopped position of thethird lens group 13 is also “the wide angle position plus “X”” inconsideration of the overrun of the first and second lens groups 11 and12. A value of the “X” is obtained by a linear calculation depending onpulse numbers between the zooming positions of the first and second lensgroups 11 and 12, the overrun amount, and a pulse number between thezooming positions of the third lens group 13. The zooming position isone of sections divided into 16 equally between the wide angle positionand the telephoto position (between W and T).

The drive of the fourth frame pulse motor 508 in the direction of a wideangle infinite position is initiated when the drive of the first andsecond lens groups 11 and 12 is completed, the reference position (HPposition) of the third lens group 13 is detected, and the third lensgroup 13 is driven more than the specified pulse number. If the drive ofthe first and second lens groups 11 and 12 is not completed, or thethird lens group 13 is not driven more than the specified pulse from thereference position, a standby state is set until the drive of the firstand second lens groups 11 and 12 is completed as well as the third lensgroup 13 is driven more than the specified pulse from the referenceposition. When the fourth frame pulse motor 508 is driven in the statethat the drive of the first and second lens groups 11 and 12 are notcompleted, the three motors are driven simultaneously and consequently,current consumption increases. Therefore, in such a case, only the thirdand fourth lens groups are driven simultaneously. Moreover, when thefourth lens group 14 is driven before the third lens group 13 reachesthe position more than the specified pulse number, the interferencebetween the third and fourth lens groups 13 and 14 occurs. Therefore,the drive of the fourth lens group 14 is initiated after the third lensgroup 13 is driven more than the specified pulse number.

The fourth lens group 14 is waited for detecting the reference positionby the fourth frame photo-interrupter 512. In addition, the drivevoltage of the fourth frame pulse motor 508 is set to be lower than thatof the normal drive so as to reduce the current consumption. A placewhere the reference position signal (HP signal) by the fourth framephoto-interrupter 512 has changed from the L to the H becomes thereference position (HP position) of the fourth lens group 14. When thereference position (HP position) of the fourth lens group is detected,positional information of the fourth lens group 14 is reset. In thisembodiment, the HP position of the fourth lens group 14 is configured tobe detected by way of detecting the position of the forth fame 41. Thefourth lens group 14 is pulse-driven according to the detected referenceposition (HP position) by the fourth frame pulse motor 508 on the basisof the movement amount to the wide angle infinite position. The wideangle infinite position is previously set, but it can be changed bystoring it in a nonvolatile memory such as the EEPROM or the like andrewriting it.

In the embodiment, as described above and shown in the timing chart ofFIG. 22, the number of motors driven simultaneously can be limited up totwo so as to reduce the current consumption as well as to shorten thetime required for activation by the optimum drive of the motors.

Next, a case in which the barrier switch signal is changed in a closedstate during a period for monitoring the barrier switch immediatelyafter the activation of the first and second frames DC motor 503 isinitiated is described with reference to FIG. 23. If the barrier switchsignal is changed from the opened state to the closed state during theperiod, the drive of the first and second frames DC motor 503 isstopped. Thereafter, the drive of the first and second frames DC motor503 by a movement amount or by the specified pulse number toward thedirection of the collapsed position is initiated. In this case, thedrive voltage is made lower so as to prevent generation of breaking anddamage even if operating parts of the lens barrier hit against the firstand second lens groups and so on in the end of the collapsed position.By such a control, the first and second lens groups are prevented frominterfering with the lens barrier.

[Reset Sequence]

Moreover, if the detected result of the first and second photo-reflector510 is not the collapsed position (reference position HP, signal=L), thedetected result of the third frame photo-interrupter 351 is not thecollapsed position (reference position HP, signal=H), or the detectedresult of the fourth frame photo-interrupter 512 is not the collapsedposition (reference position HP, signal=H), the reset sequence drive isexecuted. The reset sequence is described referring to FIGS. 24A and24B, wherein FIG. 24A is a table showing the reset sequence of the lensbarrel, and FIG. 24B is a timing chart of the HP signals.

When first and second group HP signal=H, third group HP signal=L, fourthgroup HP signal=L>

First, as the reset operation of the first and second lens groups 11 and12, the reference position (HP position) of the first and second lensgroups 11 and 12 is detected, and the first and second lens groups 11and 12 are moved to the wide angle position (first and second groups:Reset). Next, as the storing operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group is moved to the collapsed position(fourth group: Storage). Subsequently, as the reset operation of thethird lens group 13, the reference position (HP position) of the thirdlens group 13 is detected, and the third lens group is moved to the wideangle position (third group: Reset). Finally, as the reset operation ofthe fourth lens group 14, the reference position (HP position) of thefourth lens group 14 is detected, and the fourth lens group 14 is movedto the wide angle infinite position (fourth group: Reset).

<When first and second group HP signal=H, third group HP signal=L,fourth group HP signal=H>

First, as the retiring operation of the first and second lens groups 11and 12, the first and second lens groups 11 and 12 are driven in thedirection of the telephoto and pulse-driven by the specified pulse afterthe lowering of the reference signal is detected (first and groups;Retire). Next, as the storing operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the collapsedposition (fourth group: Storage). Subsequently, as the reset operationof the first and second lens groups 11 and 12, the reference position(HP position) of the first and second lens groups 11 and 12 is detected,and the first and second lens groups 11 and 12 are moved to the wideangle position (first and second groups: Reset). Next, as the resetoperation of the third lens group 13, the reference position (HPposition) of the third lens group 13 is detected, and the third lensgroup 13 is moved to the wide angle position (third group: Reset).Finally, as the reset operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the wide angleinfinite position (fourth group: Reset).

<When first and second group HP signal=H, third group HP signal=H,fourth group HP signal=L>

<When first and second group HP signal=H, third group HP signal=H,fourth group HP signal=H>

First, as the retiring operation of the first and second lens groups 11and 12, the first and second lens groups 11 and 12 are driven in thedirection of the telephoto and pulse-driven by the specified pulse afterthe lowering of the reference signal is detected (first and groups;Retire). Next, as the storing operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the collapsedposition (fourth group: Storage). If the reference position (HPposition) of the fourth lens group 14 can be detected, the referenceposition (HP position) of the third lens group 13 is detected and thethird lens group 13 is moved to the collapsed position as the storingoperation of the third lens group 13 (third group: Storage). If thereference position (HP position) of the fourth lens group 14 cannot bedetected, because it is considered that the fourth lens group 14 isinterfered with the third lens group 13, the storing operation of thethird lens group 13 is previously carried out (third group: Storage). Ifthe storing operation of the third lens group 13 is completed, thestoring operation of the fourth lens group 14 is then carried out(fourth group: Storage). If the HP position is not detected at the timeof operating the storage of the third lens group 13, because it isconsidered that the third lens group 13 is interfered with the fourthlens group 14, the third lens group 13 is driven by the specified pulsecount in the direction of the telephoto as the retiring operation of thethird lens group 13 (third group: Retire). Thereafter, the storingoperation (fourth group: Storage) of the fourth lens group 14 and thestoring operation (third group: Storage) of the third lens group 13 arecarried out. Subsequently, as the reset operation of the first andsecond lens groups 11 and 12, the reference position (HP position) ofthe first and second lens groups 11 and 12 is detected, and the firstand second lens groups 11 and 12 are moved to the wide angle position(first and second groups: Reset). Next, as the reset operation of thethird lens group 13, the reference position (HP position) of the thirdlens group 13 is detected, and the third lens group 13 is moved to thewide angle position (third group: Reset). Finally, as the resetoperation of the fourth lens group 14, the reference position (HPposition) of the fourth lens group 14 is detected, and the fourth lensgroup 14 is moved to the wide angle infinite position (fourth group:Reset).

<When first and second group HP signal=L, third group HP signal=L,fourth group HP signal=L>

<When first and second group HP signal=L, third group HP signal=L,fourth group HP signal=H>

First, as the storing operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the collapsedposition (fourth group: Storage). Next, as the storing operation of thethird lens group 13, the reference position (HP position) of the thirdlens group 13 is detected, and the third lens group 13 is moved to thecollapsed position (third group: Storage). Next, as the reset operationof the first and second lens groups 11 and 12, the reference position(HP position) of the first and second lens groups 11 and 12 is detected,and the first and second lens groups 11 and 12 are moved to the wideangle position (first and second groups: Reset). Subsequently, as thereset operation of the third lens group 13, the reference position (HPposition) of the third lens group 13 is detected, and the third lensgroup 13 is moved to the wide angle position (third group: Reset).Finally, as the reset operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the wide angleinfinite position (fourth group: Reset).

<When first and second group HP signal=L, third group HP signal H,fourth group HP signal=I

<When first and second group HP signal=L, third group HP signal=H,fourth group HP signal=H>

First, as the storing operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the collapsedposition (fourth group: Storage). If the reference position (HPposition) of the fourth lens group 14 can be detected, as the storingoperation of the third lens group 13, the reference position (HPposition) of the third lens group 13 is detected, and the third lensgroup 13 is moved to the collapsed position (third group: Storage).

If the reference position (HP position) of the fourth lens group 14cannot be detected, because it is considered that the fourth lens group14 is interfered with the third lens group 13, the storing operation ofthe third lens group 13 is previously carried out (third group:Storage). If the storing operation of the third lens group 13 iscompleted, the storing operation of the fourth lens group 14 is thencarried out (fourth group: Storage).

If the HP position is not detected at the time of operating the storageof the third lens group 13, because it is considered that the third lensgroup 13 is interfered with the fourth lens group 14, the third lensgroup 13 is driven by the specified pulse count in the direction of thetelephoto as the retiring operation of the third lens group 13 (thirdgroup; Retire). Thereafter, the storing operation (fourth group:Storage) of the fourth lens group 14 and the storing operation (thirdgroup: Storage) of the third lens group 13 are carried out.

Subsequently, as the reset operation of the first and second lens groups11 and 12, the reference position (HP position) of the first and secondlens groups 11 and 12 is detected, and the first and second lens groups11 and 12 are moved to the wide angle position (first and second groups:Reset). Next, as the reset operation of the third lens group 13, thereference position (HP position) of the third lens group 13 is detected,and the third lens group 13 is moved to the wide angle position (thirdgroup: Reset). Finally, as the reset operation of the fourth lens group14, the reference position (HP signal) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the wide angleinfinite position (fourth group: Reset).

[Storing Sequence]

The barrier switch signal changes from L to H by closing the lensbarrier 62 to initiate the storing operation. Meanwhile, the barrierswitch may be operated by mechanically closing the lens barrier 62 bymeans of an operating lever or the like, or the lens barrier 62 may beclosed by operation of the barrier switch.

The shutter of the shutter/aperture stop unit 15 is set in the fullyclosed state through the full closing control of the shutter by theshutter motor 506. Next, the aperture stop of the shutter/aperture stopunit 15 is set in the intermediately restricted state through theintermediate restricting control of the aperture stop by the first andsecond aperture stop driving motors 504 and 505. Subsequently, thestoring drive of the fourth lens group 14 is achieved through the fourthframe pulse motor 508. The standby for detecting the reference positionof the fourth frame pulse motor 508 by the fourth framephoto-interrupter 512 is set after the drive of the fourth frame pulsemotor 508 to the collapsed position is initiated.

The fourth frame pulse motor 508 is pulse-driven by the movement amountto the collapsed position from the place where the reference positionalsignal (HP signal) by the fourth frame photo-interrupter 512 changesfrom H to L. The movement amount to the collapsed position is previouslyset, but the movement amount can be changed by storing it in thenonvolatile memory such as the EEPROM or the like and rewriting it.

Next, the drive of storing the third lens group 13 is executed throughthe third frame pulse motor 507. The third lens group 13 is waited fordetecting the reference position by the third frame photo-interrupter511 by initiating the drive of the third frame pulse motor 507 in thedirection of the collapsed position.

The third lens group 13 is pulse-driven by the movement from the placewhere the reference position signal (HP signal) by the third framephoto-interrupter 511 has changed from H to L to the collapsed position.Although the movement amount to the collapsed position is setpreviously, the movement amount can be changed by storing it in thenonvolatile memory such as the EEPROM or the like and rewriting it.

The drive pulse rate of the third frame pulse motor 507 between thereference position and the collapsed position is lower than the drivepulse rate until the reference position. In this way, a smooth pulsedrive can be accomplished by changing the pulse rate in accordance withan area in which a torque is necessary.

Next, the drive of storing the first and second lens groups 11 and 12 isexecuted through the first and second frames DC motor 503. The first andsecond lens groups 11 and 12 are waited for detecting the referenceposition by the first and second frames photo-reflector 510 byinitiating the drive of the first and second frames DC motor 503 in thedirection of the collapsed position. The control for the movement amountof the first and second lens groups 11 and 12 is achieved by countingthe pulse-like signal (PI signal) by the first and second framesphoto-interrupter 509 to acquire the movement amount from the placewhere the reference position signal (HP signal) by the first and secondframes photo-reflector 510 has changed from L to H to the collapsedposition. Although the movement amount to the collapsed position is setpreviously, the movement amount can be configured to be changed bystoring it in the nonvolatile memory such as the EEPROM or the like andrewriting it.

In the drive for storing the first and second lens groups 11 and 12, thePI signal is counted by the first and second frames photo-interrupter609 without dropping the voltage of the first and second frames DC motor503 before stopping it, and when the first and second lens groups 11 and12 reach the collapsed position, a breaking control is achieved in orderto stop the drive of the first and second lens groups 11 and 12. This isto prevent the first and second group DC motor from stopping at themiddle of the drive due to the dropping of voltage.

[Changing Magnification Sequence]

A sequence for operating a changing magnification is described withreference to a flow chart shown in FIG. 26.

When a changing magnification process is initiated by operating a zoomlever, zoom button or the like, whether it is necessary to retire thefourth lens group 14 is determined (step S11). It is determined in thestep S11 that the retire process for the fourth lens group 14 isrequired if the fourth lens group 14 is disposed in a nearer positionthan a predetermined position in the changing magnification process fromthe telephoto to the wide angle. Next, a direction of drive of thechanging magnification is determined (step S12). If it is the changingmagnification from the wide angle to the telephoto, the drive of thefirst and second lens groups 11 and 12 is initiated by operating thefirst and second frames DC motor 503 (step S13).

Next, whether the first and second lens groups 11 and 12 are to bestopped is determined (step S14). It is determined in the step S14 thatthe first and second lens groups 11 and 12 are stopped in a casesatisfying one of conditions in which, if a zoom driving switch operatedby changing magnification manipulation through the zoom lever or zoombutton or the like becomes off; if the first and second lens groups 11and 12 reach a position in front of a predetermined amount from thetelephoto position in the drive from the wide angle to the telephoto;and if the first and second lens groups 11 and 12 reach a position infront of a predetermined amount from the wide angle position in thedrive from the telephoto to the wide angle.

If the first and second lens groups 11 and 12 are to be stopped, whetherthe third lens group 13 is driving is judged (step S15). If the thirdlens group 13 is stopping, the stopping operation of the first andsecond lens groups 11 and 12 is executed (step S16) and the breakingoperation of the first and second lens groups 11 and 12 is executed(step S17). Subsequently, the driving direction of the changingmagnification is determined (step S18). If it is the changingmagnification from the wide angle to the telephoto, drive for correctinga position of the third lens group 13 is achieved (step S19), the driveof the aperture stop is executed (step S20), and the process iscompleted and returned from the step S20 to a process waiting state.

If it is determined that the retire process of the fourth lens group 14is determined to be required in the step S11, the retire process of thefourth lens group 14 is executed (step. S21), and the process is shiftedfrom the step S21 to the step S12. In the step S12, if it is determinedthat the changing magnification driving direction is the changingmagnification from the telephoto to the wide angle, the retire processof the third lens group 13 is executed (step S22), and the process isshifted from the step S22 to the step S14.

In the step S14, if it is determined that the first and second lensgroups 11 and 12 continue to drive without stopping them, whether thethird lens group 13 is driving is judged (step S23). If the third lensgroup 13 is stopping, whether the drive of the third lens group 13 isinitiated is determined (step S24). It is determined in the step S24that the drive of the third lens group 13 is permitted in a casesatisfying one of conditions in which: if the first and second lensgroups 11 and 12 are driven more than the specified driven amount afterthe initiation of the drive of the first and second lens groups 11 and12; if the position of the third lens group 13 is away by apredetermined amount or more from the position of the first and secondlens groups 11 and 12 when the first and second lens groups 11 and 12pass a predetermined zooming point in the driving state that the thirdlens group 13 is re-driven from the wide angle to the telephoto; and ifthe position of the third lens group 13 is approaching a predeterminedamount or more to the position of the first and second lens groups 11and 12 when the first and second lens groups 11 and 12 pass apredetermined zooming point in the driving state that the third lensgroup 13 is re-driven from the telephoto to the wide angle. If the driveof the third lens group 13 is permitted in the step S24, the drive ofthe third lens group 13 is initiated (step S25), and the process isreturned from the step S25 to the step S14. If the drive of the thirdlens group 13 is not permitted in the step S24, the process is returnedfrom the step S24 to the step S14 directly.

In the step S23, if it is judged-that the third lens group 13 isdriving, whether the drive of the third lens group 13 is stopped isdetermined (step S26). It is determined in the step S26 that the thirdlens group 13 is permitted in a case satisfying one of conditions inwhich: if the position of the third lens group 13 approaches apredetermined amount or more to the position of the first and secondlens groups 11 and 12 in the drive from the wide angle to the telephoto;and if the position of the third lens group 13 is away a predeterminedor more from the position of the first and second lens groups 11 and 12in the drive from the telephoto to the wide angle. If the stop of thethird lens group 13 is permitted in the step S26, the stop of the thirdlens group 13 is initiated (step S27), and the process is returned fromthe step S27 to the step S14. In the step S26, if the stop of the thirdlens group 13 is not permitted, the process is returned the step S26 tothe step S14 directly.

In the step S15, if it is judged that the third lens group 13 isdriving, the stop of the third lens group 13 is initiated (step S28),and the process is shifted from the step S28 to the step S16. In thestep S18, if it is determined that the changing magnification drivingdirection is the changing magnification from the telephoto to the wideangle, a backlash operation is executed (step S29), and the process isshifted from the step S29 to the step S19.

Next, a changing magnification operation according to the flow chart isexplained in detail with reference to each of the direction of changingmagnification.

[From Wide Angle to Telephoto]

First, a changing magnification operation from the wide angle to thetelephoto is described by referring to the timing chart shown in FIG.27.

By pressing down a telephoto button of the zoom button, the telephotoswitch signal changes from H to L, and thus a variable sequence to thetelephoto direction is initiated. Initially, a retire determination ofthe fourth lens group 14 is executed (step S11).

As described above, in the retire determination of the fourth lens group14, the fourth lens group 14 is retired only if both of the followingconditions are satisfied (AND condition).

(1) Changing magnification drive from telephoto to the wide angle.

(2) The fourth lens group 14 is positioned in a nearer position to thesubject (extended out position) away from a predetermined position(retired threshold position).

However, because the above-mentioned conditions are not satisfied in thedrive from the wide angle to the telephoto, the fourth lens group 14 isnot retired.

Next, in the driving direction, whether the third lens group 13 is to beretired is determined (step S12). In the case of the changingmagnification drive from the wide angle to the telephoto, the retiringdrive of the third lens group 13 is not necessary. The drive of thefirst and second lens groups 11 and 12 is initiated through the firstand second frames DC motor 503 (step S13). In an actuating periodimmediately after the initiation of activation of the first and secondframes DC motor 503, the drive voltage is set to be lower than thestationary voltage in order to prevent the rush current by the first andsecond group DC motor. After the activation period is lapsed, the drivevoltage is increased to the stationary voltage. The drive voltagebetween the wide angle and the telephoto is set to be lower than thatbetween the collapsed position and wide angle position. This is for thereason that a higher speed is required between the stored and wide anglepositions, and hence a higher voltage is set, while a suitable voltagesetting is made between the wide angle and the telephoto so as to allowthe first and second frames DC motor 503 to stop at a desired positionby operation of the zoom button. The control of the movement amount ofthe first and second lens groups 11 and 12 is achieved by counting thepulse-like signal (PI signal) by the first and second framesphoto-interrupter 509. The zooming points each of which is a controlreference position are set in 17 points in which a distance between thewide angle and the telephoto is divided into 16 equally.

Next, whether the first and second lens groups 11 and 12 are to bestopped is determined (step S14). In the determination for stopping thedrive of the first and second lens groups 11 and 12, if either one ofthe following conditions is satisfied (OR condition), a stopping processis executed.

(1) A telephoto zooming drive switch operated by the changingmagnification operation through the zoom lever or zoom button or thelike is turned off, i.e. changed from L to H.

(2) The first and second lens groups 11 and 12 reach a position in frontof the telephoto position when driving from the wide angle to thetelephoto.

In a case that the driving of the first and second lens groups 11 and 12is continuing, the judgment of driving initiation/driving stop of thethird lens group 13 is executed in response to the status (duringdriving or stopping) of the third lens group 13 (step S23). If the thirdlens group 13 is stopping, the determination of drive initiation of thethird lens group 13 is executed (step S24), and if the initiation ispermitted, the drive of the third lens group 13 is initiated. In thestep S24, the drive of the third lens group 13 is initiated if eitherone of the following conditions is satisfied.

(1) The first and second lens groups 11 and 12 are driven by thespecified driven amount or more after the initiation of the drive of thefirst and second lens groups 11 and 12.

(2) During the third lens group 13 is re-driving in the drive from thewide angle to the telephoto, the position of the third lens group 13 isaway by a predetermined amount from the position of the first and secondlens groups 11 and 12 when the first and second lens groups 11 and 12pass a predetermined zooming point.

Moreover, if the third lens group 13 is driving, whether the third lensgroup 13 is to be stopped is determined (step S26), and if the stop ispermitted, the drive of the third lens group 13 is stopped. In thedetermination whether the third lens group 13 is to be stopped, thethird lens group 13 is stopped if the condition that: the position ofthe third lens group 13 is positioned closer than the predetermineamount to the position of the first and second lens groups 11 and 12 inthe drive from the wide angle to the telephoto, is satisfied.

More specifically, when the first and second lens group 11 and 12 areactivated and the driven amount of the first and second lens groups 11and 12 becomes the specified pulse or more, the drive of the third lensgroup 13 is initiated. During simultaneous drive of the first, secondand third lens groups, if the position of the third lens group 13approaches by the predetermined amount to the position of the first andsecond lens groups 11 and 12, the drive of the third lens group 13 isstopped. Thereafter, when the first and second lens groups 11 and 12 areaway from the third lens group 13 and they are away from the third lensgroup 13 by a predetermined amount, the drive of the third lens group 13is re-started. The drive and stop of the third lens group 13 arerepeated in response to a positional relationship among the first andsecond lens groups 11 and 12, and the third lens group 13. Thereby, itis possible to achieve the changing magnification drive whilemaintaining a distance among the first, second, and third lens groups11, 12 and 13. When activating these lens groups, the influence of therush current caused by the first and second frames DC motor 503 can beavoided by initiating the drive of the third lens group 13 after thedrive of the specified amount or more of the first and second lensgroups 11 and 12 is carried out, and therefore the current consumptionis reduced.

If the telephoto switch signal has changed from L to H before theinitiation of the initial drive of the third lens group 13, the stop ofthe first and second lens groups 11 and 12 is controlled without thesimultaneous drive of the third lens group 13 therewith. If the firstand second lens groups 11 and 12 are stopped after the stop of them isdetermined, the stop operation of the third lens group 13 is initiatedif the third lens group 13 is driving. Then, the stop of the first andsecond lens groups 11 and 12 is also initiated. A lower speed controlperiod is set during the stop operation of the first and second lensgroups 11 and 12, so that the drive voltage of the first and secondframes DC motor 503 is lowered according to the residual pulse number toa target position. Thereby, the overrun amount of the first and secondlens groups 11 and 12 when reaching the target position is decreased. Ifthe first and second lens groups 11 and 12 reach the target position bycounting the PI signal by the first and second frames photo-interrupter509, a breaking operation is executed in order to stop the drive of thefirst and second lens groups 11 and 12. The overrun amount during theperiod of breaking is also counted to decide a final position of thefirst and second lens groups 11 and 12.

After the first and second lens groups 11 and 12 are stopped, acorrection drive for the position of the third lens group 13 isexecuted. This is to compute a stopping position of the third lens group13 corresponding to the final stopping position of the first and secondlens groups 11 and 12 and drive the third lens group 13 to the stoppingposition. A target stopping position of the third lens group 13corresponding to the stopping position of the first and second lensgroups 11 and 12 is interpolatively computed from the positionalinformation of the first and second lens groups 11 and 12 every thezooming point and the positional information of the third lens group 13every the zooming point. Thereafter, the drive of the aperture stop isachieved to set a position of the aperture stop corresponding to thestopped zooming position of the third lens group 13 (step S20).

[From the Telephoto to the Wide Angle]

Next, a changing magnification operation from the telephoto to the wideangle is described with reference to the timing chart shown in FIG. 28.

By pressing down a wide angle button of the zoom button, the wide angleswitch signal changes from H to L, and a variable sequence with respectto the wide angle direction is initiated. Initially, a retiredetermination of the fourth lens group 14 is executed.

As described above, in the retire determination of the fourth lens group14, the fourth lens group is retired only if both of the followingconditions are satisfied (AND condition).

(1) Changing magnification drive from telephoto to the wide angle.

(2) The fourth lens group 14 is positioned in a closer position to thesubject (extended out position) away from a predetermined position(retired threshold position).

If the position of the fourth lens group 14 is in the nearer positionthan the predetermined position when driving from the telephoto to thewide angle, the fourth lens group 14 is retired. The retired amount isset to a range in which the third lens group 13 does not interfere withthe fourth lens group 14 in the variable operation of the third lensgroup 13.

Next, the third lens group 13 is retired. In order to prevent theinterference of the third lens group 13 with the first and second lensgroups 11 and 12 due to the initiation of the drive of the first andsecond lens groups 11 and 12, the third lens group 13 is drivenpreviously by the specified amount. The drive of the first and secondlens groups 11 and 12 is then initiated through the first and secondframes DC motor 503.

As described above, in the activation period immediately after theinitiation of activation of the first and second frames DC motor 503,the drive voltage is set to be lower than the stationary voltage inorder to prevent the rush current by the first and second frames DCmotor 503. After the activation period is lapsed, the drive voltage isincreased to the stationary voltage. The control of the movement amountof the first and second lens groups 11 and 12 is achieved by countingthe pulse-like signal (PI signal) by the first and second framesphoto-interrupter 509. As described above, the zooming points each ofwhich is a control reference position are set in 17 points in which adistance between the wide angle and the telephoto is divided into 16equally.

In the determination for stopping the drive of the first and second lensgroups 11 and 12, if either one of the following conditions is satisfied(OR condition), the stopping process is executed, as described above.

(1) A telephoto zooming drive switch operated by the changingmagnification operation through the zoom lever or zoom button or thelike is turned off, i.e., changed from L to H.

(2) The first and second lens groups 11 and 12 reach a position in frontof the telephoto position when driving from the telephoto to the wideangle.

In a case that the driving of the first and second lens groups 11 and 12is continuing, the determination of driving initiation/driving stop ofthe third lens group 13 is executed in response to the status (duringdriving or stopping) of the third lens group 13. If the third lens group13 is stopping, the determination for the initiation of drive of thethird lens group 13 is executed, and if the initiation is permitted, thedrive of the third lens group 13 is initiated. In the determination forinitiating the drive of the third lens group 13, the drive of the thirdlens group 13 is initiated if either one of the following conditions issatisfied (OR condition).

(1) The first and second lens groups 11 and 12 are driven by thespecified driven amount or more after the initiation of the drive of thefirst and second lens groups 11 and 12.

(2) During the third lens group 13 is re-driving in the drive from thetelephoto to the wide angle, and the position of the third lens group 13approaches by a predetermined amount to the position of the first andsecond lens groups 11 and 12 when the first and second lens groups 11and 12 pass a predetermined zooming point.

Moreover, if the third lens group 13 is driving, the determination forstopping the drive of the third lens group 13 is executed, and if thestop is permitted, the drive of the third lens group 13 is stopped. Inthe determination whether the third lens group 13 is to be stopped, thethird lens group 13 is stopped if the condition that: the position ofthe third lens group 13 is away by the predetermine amount or more fromthe position of the first and second lens groups 11 and 12 in the drivefrom the telephoto to the wide angle, is satisfied.

More specifically, the first and second lens group 11 and 12 areactuated, and if the driven amount of the first and second lens groups11 and 12 becomes the specified amount or more, the drive of the thirdlens group 13 is initiated. During simultaneous drive of the first,second and third lens groups 11, 12 and 13, if the position of the thirdlens group 13 is away by the predetermined amount from the position ofthe first and second lens groups 11 and 12, the drive of the third lensgroup 13 is stopped. Thereafter, when the first and second lens groups11 and 12 approach to the third lens group 13 and approach to the thirdlens group 13 by the specified amount or more, the drive of the thirdlens group 13 is re-started. The drive and stop of the third lens group13 are repeated in response to a positional relationship among the firstand second lens groups 11 and 12, and the third lens group 13. Thereby,it is possible to achieve the changing magnification drive whilemaintaining a distance among the first, second, and third lens groups11, 12, and 13. In addition, the influence of the rush current of thefirst and second frames DC motor 503 can be avoided by initiating thedrive of the third lens group 13 after the specified pulse or more iscounted from the activation of the first and second lens groups 11 and12. Thereby, it is possible to reduce the current consumption.

In the drive of the third lens group 13 to the wide angle directionduring the drive of the first and second lens groups 11 and 12,basically a control for eliminating a backlash in the movement of thethird lens group 13 is required when it is stopped. However, thebacklash eliminating control is not carried out (or prohibited) duringthe changing magnification operation so as to accomplish a smoothmovement of the third lens group 13.

If the wide angle switch signal has changed from L to H before theinitiation of the initial drive of the third lens group 13, the stop ofthe first and second lens groups 11 and 12 is controlled without thesimultaneous drive of the third lens group 13 therewith. If the firstand second lens groups 11 and 12 are stopped after the stop of them isdetermined, the stop operation of the third lens group 13 is initiatedif the third lens group 13 is driving. Then, the stop of the first andsecond lens groups 11 and 12 is also initiated.

During the stop operation of the first and second lens groups 11 and 12,a lower speed control period is set. Accordingly, the drive voltage ofthe first and second frames DC motor 503 is lowered based on theresidual pulse number to a target position. Thereby, the overrun amountof the first and second lens groups 11 and 12 when reaching the targetposition is decreased. If the first and second lens groups 11 and 12reach the target position by counting the PI signal by the first andsecond frames photo-interrupter 509, a breaking operation is executed inorder to stop the drive of the first and second lens groups 11 and 12.The overrun amount during the period of breaking is also counted todecide a final position of the first and second lens groups 11 and 12.

Furthermore, the control for eliminating the backlash of the first andsecond lens groups 11 and 12 is executed in the movement from thetelephoto to the wide angle thereof.

After the first and second lens groups 11 and 12 are stopped, acorrection drive for the position of the third lens group 13 isexecuted. This is to compute the stopping position of the third lensgroup 13 corresponding to the final stopping position of the first andsecond lens groups 11 and 12 and drive the third lens group 13 to thestopping position. A target stopping position of the third lens group 13corresponding to the stopping position of the first and second lensgroups 11 and 12 is interpolatively computed from the positionalinformation of the first and second lens groups 11 and 12 every thezooming point and the positional information of the third lens group 13every the zooming point. In the drive in the wide angle direction of thethird lens group 13, the control for eliminating the backlash of thethird lens group 13 is executed after it is stopped. Thereafter, thedrive of the aperture stop is achieved so that the aperture stop isdisposed in a position corresponding to the stopped zooming position ofthe third lens group 13.

In this example, the drive voltage of the first and second frames DCmotor 503 when it is driven in the wide angle direction is set to behigher than that in the telephoto direction in the changingmagnification operation between the wide angle and the telephoto. Thepulse rate of the third frame pulse motor 607 in the wide angledirection is set to be faster than that in the telephoto direction. Anintermittent control for the third lens group 13 is accomplished basedon the positional relationship among the first, second, and third lensgroups 11, 12, and 13 in order to maintain the distance among the first,second, and third lens groups 11, 12, and 13. Therefore, the drive speedof the third lens group 13 is set to be the same as or faster than thedrive speed of the first and second lens groups 11 and 12, in themovement in the telephoto direction. Similarly, the drive speed of thethird lens group 13 is also set to be the same as or faster than thedrive speed of the first and second lens groups 11 and 12, in themovement in the wide angle direction. With such a structure, the thirdlens group 13 is driven so that the third lens group 13 is not separatedaway from the first and second lens groups 11 and 12 in the movement inthe telephoto direction, and is not caught up by the first and secondlens groups 11 and 12 in the movement in the wide angle direction. Inthis embodiment, the drive-restarting timing of the third lens group 13is set at a specific zooming point passing time. It may be set at everytime when the pulse signal (PI signal) generated with the first andsecond photo interrupter 509 at the time of driving the first and secondlens groups 11˜12 is detected or every given counts of PI signals.Thereby, finer intermittent control can be made to enhance intergroupaccuracy.

As shown in FIG. 9, the solid image pickup element 16 such as CCD(Charge Coupled Device) is arranged behind the fourth lens group 14 thatis on a side remoter from the subject. An image of the subject isfocused on an input plane of this solid pickup device 16. Depending uponnecessity, various optical filters such as a cover glass 18, a low-passfilter 19, and other optical elements are appropriately arranged on theinput side of the solid pickup element 16.

Here, a lens barrier 62 for protecting the lens barrel is described asfollows. The lens barrier 62 shown in FIG. 3 to FIG. 5 is disposed tocover a side of the first lens group 11 facing the subject, in thestored state, and protects the lens group from contaminations ordamages. The lens barrier 62 is moved in back and forth directionstransverse to the optical axis by a barrier drive system 63. FIGS. 3 and4 show a state in which the lens barrier 62 is closed, and FIG. 5 showsa state in which the lens barrier 62 is almost opened. The barrier drivesystem 63 drives the lens barrier 62 between the closed position (FIGS.3 and 4) and the opened position (a position farther from the opticalaxis than the position shown in FIG. 5) through the operation of abarrier-operating element (see a barrier-operating element 301 in FIG.17A). The barrier drive system 63 has a function to bias the lensbarrier 62 in a closing direction at the closed position and in anopening direction at the opened position.

Therefore, when driving the lens barrier 62 in the closed state towardthe opening direction, the lens barrier 62 is moved to the opened statesemi-automatically when the lens barrier 62 passes a predeterminedposition. Also, when an attempt is made to close the lens barrier 62from the opened state, the lens barrier 62 is semi-automatically movedto the closed state semi-automatically when the lens barrier 62 passes apredetermined position. The position in the closed state is notnecessarily required to be the same as the predetermined position in theopened state; rather, it is preferable that the lens barrier has acertain degree of hysteresis characteristics in the movement toaccomplish a smooth operation of the lens barrier 62.

A barrier control member 61 is provided on a side of the fixed frame 21in the direction of opening the lens barrier 62 so as to be capable ofsliding in a direction along the optical axis, and is biased toward thesubject by a spring or the like as needed. In the stored state, anengaging portion of the barrier control member 61 which is formed into abent shape engages with base edge surfaces of the first rotary cylinder22 and the first liner 23 and is biased toward the image surface againstbiasing force of the spring, and hence is not in contact with the lensbarrier 62. In the used or photographing state, the lens barrier 62 iscompletely away from the respective lens groups and retaining framesthereof. In this state, engagement of the engaging portion of thebarrier control member 61 is released, and hence the barrier controlmember 61 is biased toward the subject by the biasing force, and then, abarrier-intercepting portion at the distal end enters into a passage ofthe lens barrier 62.

In this state, when the lens barrier 62 is rapidly operated to move thelens barrel to the collapsed position, there is a possibility that thelens barrier 62 hits against the lens barrel. However, since thebarrier-intercepting portion at the distal end of the barrier controlmember 61 crosses the passage of the lens barrier 62 to prevent the lensbarrier 62 from entering into a moving passage of the lens barrel. Whenthe respective lens groups are stored and the stored state is completed,the base edge surfaces of the first rotary cylinder 22 and the firstliner 23 engage with the engaging portion of the barrier control member61, which is formed into the bent shape, to energize the engagingportion toward the image surface against the biasing force. Therefore,the lens barrier 62 can be moved to the front portion of the lensbarrel, and hence the lens barrier 62 is correctly set to the closedposition. In this manner, the interference between the lens barrier 62and the lens cylinders retaining the lens groups can be effectivelyprevented.

In the above-mentioned embodiments, the structure in which the thirdlens group 13 is retracted out the lens cylinder unit transverse to theoptical axis X has been described. In this structure, the retractedthird lens group 13 has the minimum outer diameter. When the third lensgroup 13 having the minimum outer diameter is retracted, a projectivesize of the lens barrel in which the third lens group 13 is retractedcan be minimized efficiently, and thus the thickness of the lens barrelcan be reduced. Moreover, when the retracted lens is extended out of thefixed frame, a size of the device (at least one of the length of themain shaft and that of the lead screw) for driving the retired lensgroup (i.e. the third lens group) is minimized by taking a structuresuch that the retracted lens is not away from the imaging planepossibly. Furthermore, the lens retaining frame of the third lens group13 or the third lens group 13 itself is larger than the lens retainingframes of the other lens groups 11, 12, 14 or the other lens groups 11,12, 14 in length along the optical axis X, i.e., thickness. When thethickness of the third lens group 13 is larger than that of the otherlens groups 11, 12, and 14, consequently, the thickness of the otherlens groups decreases. Therefore, the thickness of the lens barrel canbe reduced when the lens barrel is in the collapsed position. As aresult, the thickness of the lens barrel or a size in the direction ofthe optical axis of the lens barrel is minimized. In addition, becausethe retract lens group or the third lens group 13 is disposed behind andadjacent the shutter having the aperture stop function, the diameter ofthe lens barrel is less, and the retraction of the third lens group 13is simplified without considering the interference of the shutter withthe lens group unit and separating the position of the shutter from thelens cylinder unit, excessively.

Next, a structure of the plurality of lens groups is explained infurther detail. Note that the following structure or arrangement of theplurality of lens groups is exemplary, and that the structure orarrangement of the plurality of lens groups may be appropriatelymodified. The first lens group 11 has a positive power, the second lensgroup 12 has a negative power, the third lens group 13 has a positivepower, and the fourth lens group 14 has a positive power. A changingmagnification operation is achieved by changing at least one ofintervals between the first and second lens groups 11 and 12, betweenthe second and third lens groups 12 and 13, and between the third andfourth lens groups 13 and 14. A focusing operation is achieved by movingthe fourth lens group 14 along the optical axis X to correct theposition of the image plane to the image pickup plane. Theshutter/aperture unit 15 is disposed between the second lens group 12and the third lens group 13. In other words, the shutter having thefunction of the aperture stop is positioned in front of the third lensgroup 13. The four lens groups are provided in the lens cylinder unit.Because the third lens group having the minimum outer diameter isretracted out of the lens cylinder unit without separating from theimage plane excessively, the retraction of the third lens group 13 canbe accomplished with the minimum movement and the outer diameter of thelens barrel can be minimized. In addition, the thickness of the lensbarrel is decreased by retraction of at least one lens group.Furthermore, it is possible to provide a compact lens barrel having ahigh changing magnification ratio, 4 times or more. Meanwhile, the lensgroups may be structured from a first lens group having a positivepower, a second lens group having a negative power, and a third lensgroup having a positive power, and the third lens group may beretracted. Alternatively, the lens groups may be structured by a firstlens group having a negative power, a second lens group having apositive power, and a third lens group having a positive power, and thesecond lens group or the third lens group may be retracted. Each of thelens groups may be structured from one or more lenses, and the lensgroups herein indicate integral one or more lenses. Therefore, all thelens groups may be structured by one lens, respectively.

As mentioned above, the third frame 31 retaining the third lens group 13receives the moment force of the compression torsion spring 37 placedaround the third group main-guide shaft 32. In the photographing state,the third lens group 13 is retained such that the stopper 31 a formed atthe third frame 31 is brought into contact with the third groupsub-guide shaft 33 in parallel to the third group main-guide shaft 32with the urging force of the compression torsion spring 37. Contactbetween the third group sub-guide shaft 33 and the stopper 31 a retainsthe third lens group 13, on the photographing optical axis, held by thethird lens group 13 retained by the third frame 31.

However, if an external force such as vibration overcoming the momenturging force of the compression torsion spring 37 acts upon the thirdframe 31 in the photographing state and so the third frame 31 is movedto space the third group sub-guide shaft 33 from the stopper 31 a, theoptical axis of the third lens group retained by the third frame may bedeviated from the optical axis of the other lens groups 11, 12 and 14positioned along the photographing optical axis.

In order to assuredly prevent the third lens group 13 from thephotographing optical axis with the external force such as vibration, asshown in FIGS. 29 and 30, an engaging portion 31 g engageable with thethird group sub-guide shaft 33 f is formed instead of the stopper 31 a,and a diameter-reduced portion 33 a is formed at a base portion of thethird group sub-guide shaft 33. The third group sub-guide shaft 33 isfitted to the lens barrel base 82 as a stationary portion at its baseportion where the diameter-reduced portion 33 a is formed. FIG. 29 is aperspective view of the third frame 31, positioned on the photographingoptical axis, as viewed from the side of the subject. FIG. 30 is a planeview of an area shown by a two-dot chain line in FIG. 29 as viewedtoward the image plane side from an arrow A.

As shown in FIG. 29, the third frame 31 has a crank shape comprising anintermediate portion 31 h in parallel to the photographing optical axis,that is in parallel to the third group sub-guide shaft 33, a first armportion 31 i extending at right angle to the intermediate portion fromthe tip of the intermediate portion, and a second arm portion 31 jextending from the rear end of the intermediate portion 31 h toward thethird group main-guide shaft 32 and in a direction opposite to theextending direction of the first arm portion 31 i. A circular retainingportion 31 k retaining the third lens group 13 is formed at the tip ofthe first arm portion 31 i. The engaging portion 31 g is formed at aside opposite to the extending direction of the second arm portion 31 jat the rear end of the intermediate portion 31 h. The first arm portion31 i is provided with a U-shaped groove 311 to receive the third groupsub-guide shaft 33 with backlash so as to prevent interference betweenthe third group sub-guide shaft 33.

As shown in FIG. 30, the engaging portion 31 g is formed with a circularhole 31 m having an inner diameter almost equal to the outer diameter ofthe large diameter portion 33 b of the third group sub-guide shaft 33and adapted to receive the large diameter portion 33 b. A cut portion 33n is formed to open an edge portion of the circular hole 31 m. The cutportion 31 n has a width size W1 smaller than the outer diameter of thelarge diameter portion 33 b of the third group sub-guide shaft 33 andlarger than the outer diameter D1 of the diameter-reduced portion 33 a.

As shown in FIG. 30, the engaging portion 31 g receives the largediameter portion 33 b of the third group sub-guide shaft 33 at aposition where the third frame 31 retains the third lens group 13 alongthe photographing optical axis. In this state, since the vibrationaround the third group main-guide shaft 32 is restricted with thecircular hole 31 m of the engaging portion 31 g, the optical axis of thethird lens group 13 is not so largely vibrated as to be deviated fromthe photographing photographing optical axis even if vibrationovercoming the moment urging force of the compression torsion spring 37acts upon the third frame 31. Thus, the third lens group 13 is permittedto move along the photographing optical axis.

The engaging portion 31 g engages with the diameter-reduced portion 33 aof the third group sub-guide shaft 33 at a place where the third lensgroup 13 is retracted from the photographing optical axis. Since theouter diameter D1 of the diameter-reduced portion 33 a is smaller thanthe width W of the cut portion 31 n, the engaging portion 31 g can bereleased from the third sub-guide axis 33 through the cut portion 31 nof the engaging portion 31 g.

As a result, since the sub-guide shaft member 33 for guiding the thirdlens group 13 retained by the third lens group frame 31 along the otherlens groups 11, 12, 14 is engaged with the engaging portion 31 gprovided at the retractable lens retaining frame 31, the third frame 31is permitted to move on the third group main-guide shaft 32 along thesub-guide shaft member 33 excluding the retracted point so that thethird frame can be assuredly prevented from moving away from thesub-guide shaft member. In addition, since the third frame 31 is allowedat the retracting point to move to its retracted position through thecut portion 31 n as the opened portion provided at the engaging portion31 g of the third frame 31, no restraining member is newly added torestrain the third frame 31 from moving away from the sub-guide shaftmember on photographing. Therefore, the retractable lens retaining framecan be assuredly prevented from moving away from the sub-guide shaftmember on photographing without causing complicated construction due tothe addition of such a new member, so that shake of the optical axis ofthe retractable lens retained by the retractable lens retaining framecan be assuredly prevented on photographing.

When the third lens group 13 retained by the retractable lens retainingframe 31 is retracted out of the inner diameter of the movable lenscylinder at the retracting point, the dimension in the photographingoptical axis can be effectively reduced without considerably increasingthe size within the plane orthogonal to the photographing optical axis.

Further, the engaging portion 31 g provided in the retractable lensretaining frame 31 can be more assuredly and smoothly removed throughthe opened portion 31 n of the engaging portion 31 g at the retractablelens retaining frame 31 by means of the diameter-reduced portion 33 a atsuch a portion of the sub-guide shaft member 33 as corresponding to theretracting point of the retractable lens retaining frame 31.

The sub-guide shaft member 33 is fixed to the lens barrel base 82 of thelens barrel at its base portion, and the diameter-reduced portion 33 ais formed near the base portion. Thus, the retractable lens retainingframe 31 can be assuredly moved to the retracted position in thecollapsing operation.

The retractable lens retaining frame 31 receives one-direction rotationurging force toward the photographing optical axis of the other lensgroups 11, 12, 14 as well as the urging force in the collapsingdirection along the optical axis of the other lens groups 11, 12 and 14by means of the urging element 37. Therefore, the retractable lens groupretained by the retractable lens retaining frame can be stably operatedwith further simplified construction at a lower cost and a reducedspace.

Referring now to FIG. 17A to FIG. 19, a camera including an opticalsystem device having the lens barrel according to the present inventionas shown in the first embodiment will be described as a secondembodiment. Although the lens barrel is applied to the camera here, thelens barrel is also applicable to a lens driving apparatus, an opticaldevice, etc. In addition, the lens barrel according to the presentinvention as shown in the first embodiment is also applicable to amobile information terminal such as so-called PDA (Personal DataAssistant), a mobile phone and so on, having a camera function orfunctional part installed therein.

Many of such mobile information terminals have the function and thestructure substantially identical to the function and the structure ofthe camera, although the appearance is slightly different. Therefore,the optical system device including the lens barrel according to thepresent invention may be employed in such mobile information terminals.Further, the lens barrel according to the present invention may beapplied to an image forming device such as a copying machine, a scanneror the like.

As shown in FIG. 17A, FIG. 17B and FIG. 18, the camera includes an imagepickup lens 101, a shutter button 102, a zoom lever 103, a finder 104, astrobe light 105, a liquid crystal display (LCD) 106, an operatingbutton 107, a power switch 108, a memory card slot 109, an expansioncard slot 110, the barrier-operating element 301 and so on. Furthermore,as shown in FIG. 19, the camera also includes a photodetector 201, asignal-processing unit 202, an image-processing unit 203, a centralprocessing unit (CPU) 204, a semiconductor memory 205, and an expansioncard 206. Although it is not shown specifically, electric power issupplied from a battery as an electric source to the above-mentionedparts to operate the parts.

The photodetector 201 serves as an area sensor such as a CCD (ChargeCoupled Device) image pickup element or the like to read an image of asubject to be photographed, that is, of an photographing subject, formedby the image pickup lens 101, which is a photographing optical system.As the image pickup lens 101, the optical system device including thelens barrel according to the present invention as described in the firstembodiment is employed. More specifically, the optical system deviceincludes a plurality lens groups as optical elements and a telescopiccylinder unit retaining the lens groups, which structure the lensbarrel. The lens barrel has a mechanism of retaining the respective lensgroups in the lens cylinder such that the lens groups can be moved inresponse to the movement of the lens cylinder along the optical axis ofthe lens groups, similarly to the above-mentioned embodiment. The imagepickup lens 101 to be integrated in the camera is generally integratedin the form of this optical system device.

An output from the photodetector 201 is processed by thesignal-processing unit 202, which is controlled by the centralprocessing unit 204, and is converted into digital image information.The image information digitized by the signal-processing unit 202 issubjected to a predetermined image processing in the image-processingunit 203 which is also controlled by the central processing unit 204,and then stored in the semiconductor memory 205 such as a non-volatilememory. In this case, the semiconductor memory 205 may be a memory cardinserted in the memory card slot 109, or may be a semiconductor memoryintegrated in a body of the camera. The liquid crystal display 106 maydisplay the photographing image or may display the image stored in thesemiconductor memory 205. An image stored in the semiconductor memory205 can be transmitted to the outside of the camera via the expansioncard 206 inserted in the expansion card slot 110. Meanwhile, theabove-mentioned central calculation processing device 601 shown in FIG.21 to control the drive of the lens groups may be included in thecentral processing unit 204, otherwise structured by use of othermicro-processor connecting with the central calculation processingdevice 501.

The image pickup lens 101 is embedded within the camera body into acollapsed or stored state as shown in FIG. 17A when being transported orcarried by a user, and the lens barrier 62 is closed. When the useroperates the barrier-operating element 301 to open the lens barrier 62,the power is turned on and the lens barrel is moved from the closedposition to an opened position and projected from the camera body asshown in FIG. 17B, so that the photographing state is established. Atthis time, the image pickup lens 101 within the lens barrel is set sothat the respective lens groups of the optical systems structuring azoom lens are arranged, for example, at a short focal length wide angleposition. When the zoom lever 103 is operated, the arrangement of therespective lens groups in the optical system is changed through themovement of the lens groups along the optical axis, and therefore, thezoom can be varied to the telephoto position.

Preferably, an optical system of the finder 104 is configured such thatthe zooming is varied in association with the change of the angle offield of the image pickup lens 101.

In many cases, focusing is achieved by half-pressing operation of theshutter button 102. The focusing with the zoom lens in the lens barrelaccording to the present invention is achieved mainly by moving thefourth lens group 14, although it is not limited thereto. When theshutter button 102 is further pressed to a completely pressed state, thephotographing is achieved, and subsequently the processing as describedabove is performed.

In order to display the image stored in the semiconductor memory 205 onthe liquid crystal display 106 or transmit the same to the outside ofthe camera via the expansion card 206, the operating button 107 isoperated in a predetermined manner. The semiconductor memory 205 and thecommunication card 0.206 or the like are used by being inserted in aspecific or multi-purpose slot such as the memory card slot 109 and thecommunication car slot 110.

When the image pickup lens 101 is in the stored state, the third lensgroup 13 is retracted from the optical axis to the retracted positionoutside of the telescopic cylinder unit, and hence is stored in a linewith the first lens group 11 and the second lens group 12 in ajuxtaposed manner. Therefore, further reduction in thickness of thecamera is achieved.

Generally, because a finder mechanism is disposed above the lens barrel,therefore, certain camera operation is easy. Moreover, if the lensbarrel includes a zoom changing magnification mechanism, because thefinder mechanism also needs the zoom changing magnification mechanism,it is preferable that a drive source (DC motor, pulse motor or the like)for conducting the zoom changing magnification operation and atransmission mechanism (gear connecting mechanism or the like) fortransferring a driving force of the drive source to the lens groups aredisposed adjacent the finder mechanism. For example, if the findermechanism is disposed on upper and left position of the lens barrel, thedrive source and the transmission mechanism are disposed adjacent theupper and left position of the lens barrel to use a limited spaceeffectively. When the frame for the retractable lens group (third lensgroup 13 according to the embodiment) is retracted, the retaining frameis stored below the lens barrel in consideration of the left space. Thespace is lower and right position or lower and left position of the lensbarrel. In the embodiment, the space is disposed on the lower and rightposition of the lens barrel to store the retaining frame of theretracted third lens group. The above-mentioned storage part of thefixed lens cylinder-is disposed at the position. The drive source andthe transmission mechanism for driving the lens groups are disposed atthe lower and left position. As a result, a miniaturized lens barrel canbe accomplished with effective use of fourth corners, the upper and leftposition, the upper and right position, the lower and right position,and the lower and left position of a lens barrel.

When the lens barrel according to the present invention is used for thedigital camera, the size in the photographing or photographing opticalaxis of the digital camera can be effectively decreased withoutconspicuously increasing the size inside the plane orthogonal to thephotographing optical axis of the digital camera.

Furthermore, when the lens barrel according to the present invention isused in the mobile information terminal, the size in the photographingoptical axis of the mobile information terminal can be effectivelydecreased without conspicuously increasing the size inside the planeorthogonal to the photographing optical axis of the terminal.

Furthermore, when the lens barrel according to the present invention isused in the image input device such as the scanner, the size in thephotographing optical axis of the image input device can be effectivelydecreased without conspicuously increasing the size inside the planeorthogonal to the photographing optical axis of the image input device.

Although the present invention has been described in terms of exemplaryembodiments, it is not limited thereto. It should be appreciated thatvariations may be made in the embodiments described by persons skilledin the art without departing from the scope of the present invention asdefined by the following claims. Moreover, no element and component inthe present disclosure is intended to be dedicated to the publicregardless of whether the element or component is explicitly recited inthe following claims.

1. A lens barrel, comprising: a) a plurality of lens groups each having at least one lens; b) a plurality of lens retaining frames each retaining corresponding one of the plurality of the lens groups, said plurality of the lens retaining frames comprising a retractable lens retaining frame, c) lens retaining frame driving devices configured to drive the plurality of the lens retaining frames, said retractable lens retaining frame being configured to retain and move at least one lens group such that the retractable lens retaining frame aligns the corresponding at least one lens group the other along an identical optical axis in photographing state in which at least a part of the plurality of lens groups is moved toward a subject to be photographed, and retracts said corresponding at least one lens group outside a telescopic cylinder containing therein the other lens groups to a retracted position in a collapsed state in which at least a part of the plurality of the lens groups is collapsed to store the lens groups, said telescopic cylinder being constituted by movable lens cylinders for said the other lens groups, respectively; d) a main-guide shaft member which is in parallel to said optical axis of the other lens group or groups and supports the retractable lens retaining frame rotatably in longitudinal and circumferential directions of the main-guide shaft member, and e) a sub-guide shaft member configured to guide said retractable lens retaining frame along the optical axis, said sub-guide shaft member being configured to allow said retractable lens retaining frame to be retracted toward the retracted position at a retracting point on said main-guide shaft member and to guide said retractable lens retaining frame on the main-guide shaft member along said optical axis at other than the retracting point, said retractable lens retaining frame being formed with an engaging portion configured to engage with the sub-guide shaft member and to be guided along the sub-guide shaft member, and said engaging portion being formed with an opened portion configured to allow said retractable lens retaining frame to be released from the sub-guide shaft member at said retracting point.
 2. The lens barrel claimed in claim 1, wherein said movable lens cylinders retains said movable lens retaining frames therein, said movable lens retaining frames are driven by said lens retaining frame driving device via said movable lens cylinders, respectively, and said retractable lens retaining frame retracts said at least one retractable lens outside inner diameter portions of said movable lens cylinders at said retracting point.
 3. The lens barrel claimed in claim 1, wherein the sub-guide shaft member is formed with a diameter-reduced portion at a position corresponding to said retracting point of said retractable lens retaining frame, said diameter-reduced portion being configured to be released from the engaging portion through the opened portion.
 4. The lens barrel claimed in claim 2, wherein the sub-guide shaft member is formed with a diameter-reduced portion at a position corresponding to said retracting point of said retractable lens retaining frame, said diameter-reduced portion being configured to be released from the engaging portion through the opened portion.
 5. The lens barrel set forth in claim 3, wherein a base portion of said sub-guide shaft member is fixed to a stationary portion of a lens barrel body, and said diameter-reduced portion is formed near said base portion.
 6. The lens barrel set forth in claim 4, wherein a base portion of said sub-guide shaft member is fixed to a stationary portion of a lens barrel body, and said diameter-reduced portion is formed near said base portion.
 7. The lens barrel set forth in claim 1, which comprises an urging device and wherein said retractable lens retaining frame receives one direction rotation urging force toward the optical axis and an urging force toward a collapsing direction along the optical axis from the urging device.
 8. The lens barrel set forth in claim 2, which comprises an urging device and wherein said retractable lens retaining frame receives one direction rotation urging force toward the optical axis and an urging force toward a collapsing direction along the optical axis of the other lens groups from the urging device.
 9. The lens barrel set forth in claim 3, which comprises an urging device and wherein said retractable lens retaining frame receives one direction rotation urging force toward the optical axis and an urging force toward a collapsing direction along the optical axis of the other lens groups from the urging device.
 10. The lens barrel set forth in claim 4, which comprises an urging device and wherein said retractable lens retaining frame receives one direction rotation urging force toward the optical axis and an urging force toward a collapsing direction along the optical axis of the other lens groups from the urging device.
 11. The lens barrel set forth in claim 5, which comprises an urging device and wherein said retractable lens retaining frame receives one direction rotation urging force toward the optical axis and an urging force toward a collapsing direction along the optical axis of the other lens groups from the urging device.
 12. The lens barrel set forth in claim 6, which comprises an urging device and wherein said retractable lens retaining frame receives one direction rotation urging force toward the optical axis and an urging force toward a collapsing direction along the optical axis of the other lens groups from the urging device.
 13. A digital camera comprising the lens barrel claimed in claim
 1. 14. A mobile information terminal comprising the lens barrel claimed in claim
 1. 15. An image inputting device comprising the lens barrel claimed in claim
 1. 16. A digital camera comprising the lens barrel claimed in claim
 2. 17. A mobile information terminal comprising the lens barrel claimed in claim
 2. 18. An image inputting device comprising the lens barrel claimed in claim
 2. 19. A digital camera comprising the lens barrel claimed in claim
 8. 20. A mobile information terminal comprising the lens barrel claimed in claim
 3. 21. An image inputting device comprising the lens barrel claimed in claim
 3. 22. A digital camera comprising the lens barrel claimed in claim
 4. 23. A mobile information terminal comprising the lens barrel claimed in claim
 4. 24. An image inputting device comprising the lens barrel claimed in claim
 4. 